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How to write out odd numbers in an interval using for function

So my homework is I have to take two numbers from the user then I have to write out the odd numbers in that interval.But the code under doesn't work. It writes out "TrueFalseTrueFalse".
int szam;
int szam2=0;
int szam3=0;
int szam4=0;
Console.Write("Please give a number:");
szam = Convert.ToInt32(Console.ReadLine());
Console.Write("Please give another number:");
szam2 = Convert.ToInt32(Console.ReadLine());
if (szam>szam2)
{
for (szam3=szam, szam4 = szam2; szam4 < szam3; szam4++)
{
Console.Write(szam2 % 2==1);
}
}
else
{
for (szam3 = szam, szam4 = szam2; szam3 < szam4; szam3++)
{
Console.Write(szam3 % 2 ==1);
}
}
So if the two numbers would be 0 and 10, the program has to write out 1, 3, 5, 7, and 9

I would be careful when naming your variables yes its a small piece of code but it gets confusing to people trying to read it.
Based on the requirement, I would guess you want all the odd numbers given a certain range.
const string comma = ",";
static void Main(string[] args)
{
int start = getNumber();
int end = getNumber();
if(start > end)
{
int placeHolder = end;
end = start;
start = placeHolder;
}
string delimiter = string.Empty;
for(int i = start; i < end; i++)
{
if(i % 2 == 1)
{
Console.Write(string.Concat(delimiter,i.ToString()));
delimiter = comma;
}
}
Console.ReadLine();//otherwise you wont see the result
}
static int getNumber()
{
Console.Write("Please enter a number:");
string placeHolder = Console.ReadLine();
int toReturn = -1;
if (int.TryParse(placeHolder, out toReturn))
return toReturn;
return getNumber();
}
as Juharr mentioned in the comments, you need to check the result to print the actual number.

Width Linq you can write:
int szam = 20;
int szam2= 30;
var odds = Enumerable.Range(szam2 > szam ? szam : szam2, Math.Abs(szam-szam2))
.Where(x=>x % 2 != 0);
outputs:
21
23
25
27
29
// so we create a range from low to high (Enumerable.Range(..)
// take only the odd values (x % 2 != 0)
simply wrap it in string.Join to make a single string:
string text = String.Join(",",Enumerable.Range(szam2 > szam ? szam :
szam2,Math.Abs(szam-szam2))
.Where(x=>x % 2 != 0));

Logic in Change Conversion Program | indexOutOfRange [duplicate]

This question already has answers here:
What is an IndexOutOfRangeException / ArgumentOutOfRangeException and how do I fix it?
(5 answers)
Closed 5 years ago.
I'm working on a program for my C# class that is supposed to take an entered amount, as a double or not, and to find change in dollars, quarters, etc.,
I'm using the Greedy Algorithm, and I keep getting some sort of error that reads, "An unhandled exception of type 'System.IndexOutOfRangeException' occurred in 2D.exe".
I'm still relatively new to C#, and come from a Java and C++ Background.
So far I have my Money class:
using System;
using static System.Console;
namespace _2D
{
class Money
{
private double dollars, cents;
public void IncrementMoney() { }
public void DecrementMoney() { }
public Money(double dollarsncents)
{
double amountLeftOfDecimal = Math.Truncate(dollarsncents);
double amountRightOfDecimal = Math.Floor(dollarsncents);
this.dollars = Math.Round(amountLeftOfDecimal);
//the following LOGIC needs to be wokred out:
this.cents = Math.Round((amountRightOfDecimal * 100) / 100, 2);
}
public Money(int ddollars, int ccents)
{
this.dollars = ddollars;
this.cents = ccents;
}
public override string ToString()
{
return String.Format(dollars + " dollars and " + cents + " cents.");
}
public void CoinAmounts(int inAmount, int remainder, int[] coins)
{
if((inAmount % 0.25) < inAmount)
{
coins[3] = (int)(inAmount / 0.25);
remainder = inAmount % (1/4);
inAmount = remainder;
}
if ((inAmount % 0.1) < inAmount)
{
coins[2] = (int)(inAmount / 0.1);
remainder = inAmount % (1/10);
inAmount = remainder;
}
if ((inAmount % 0.05) < inAmount)
{
coins[1] = (int)(inAmount / 0.05);
remainder = inAmount % (1/20);
inAmount = remainder;
}
if ((inAmount % 0.01) < inAmount)
{
coins[0] = (int)(inAmount / 0.01);
remainder = inAmount % (1/100);
}
}
public void PrintChange(int[] arr)
{
if (arr[3] > 0)
Console.WriteLine("Number of quarters: " + arr[3]);
if (arr[2] > 0)
Console.WriteLine("Number of dimes: " + arr[2]);
if (arr[1] > 0)
Console.WriteLine("Number of nickels: " + arr[1]);
if (arr[0] > 0)
Console.WriteLine("Number of pennies: " + arr[0]);
}
}
And my Main :
using System;
namespace _2D
{
class Program
{
static void Main(string[] args)
{
Money MyMoney = new Money(23, 24);
Console.WriteLine(MyMoney.ToString());
Money dollarCentAmount = new Money(12.45);
Console.WriteLine(dollarCentAmount.ToString());
Console.WriteLine("Press any key to continue.");
Console.ReadKey();
Console.Clear();
Console.WriteLine("Enter an amount you'd like change for: ");
double inAmountDouble = Convert.ToDouble(Console.ReadLine());
int inAmount = Convert.ToInt32(inAmountDouble);
int tochange = inAmount;
int remainder = 0;
int[] coins = new int[3];
MyMoney.CoinAmounts(inAmount, remainder, coins);
Console.WriteLine(" Change for " + inAmount + " is: ");
if (inAmount > 1.0)
{
Console.WriteLine("Number of dollars: " + Convert.ToInt32(inAmount));
}
MyMoney.PrintChange(coins);
Console.ReadKey();
}
}
}

You declared coins to be an array going from 0 to 2
array[size] //size is how many elements are in the array, not the upper bound of the array
coins[3] //means the array contains three elements, elements: 0, 1, 2
//so you want:
int[] coins = new int[4]; //Goes from 0 to 3, elements: 0, 1, 2, 3
//This will allow you to later access:
//since coins[3] is the 4th element, this is as high as the array can go now
coins[3] = (int)(inAmount / 0.25);

Read() only takes first input but no other input from other Console.Read()

I am following instructions in a C# Tutorial video that is great. I am building a file with the notes and code from the video.
I reviewed similar questions but they do not solve this problem.
Here is a copy of the CS file:
static void Main(string[] args)
{
// Single line comments
/* test multi-line comments
* asldkjasldkjaskd
* asldkjasldkja
* alsdkjalksdj
* */
Console.WriteLine("Hello world!");
Console.Write("What is your name? ");
string name = Console.ReadLine();
Console.WriteLine("Hello " + name);
bool canVote = true;
char grade = 'A';
// Integer with a max number of 2,147,483,647
int maxInt = int.MaxValue;
//Long with max value of 9,223,372,036,854,775,807
long maxLong = long.MaxValue;
// Decimal has a max value of 79,228,162,514,264,337,593,543,950,335
// If you need something bigger, look up BigInteger
decimal maxDecimal = decimal.MaxValue;
// A float is a 32 bit number with a max value of 3.402823E+38 with 7 decimal positions
float maxFloat = float.MaxValue;
// A double is a 32 bit number with a max value of 1.797693134E+308 with 15 decimal positions
double maxDouble = double.MaxValue;
Console.WriteLine("Max Int : " + maxInt);
Console.WriteLine("Max Long : " + maxLong);
Console.WriteLine("Max Decimal : " + maxDecimal);
Console.WriteLine("Max Float : " + maxFloat);
Console.WriteLine("Max Double : " + maxDouble);
var anotherName = "Tom";
// anotherName = 2; Cannot implicitly convert a gype 'int' to a 'string'
Console.WriteLine("anotherName is a {0}", anotherName.GetTypeCode());
// Math
Console.WriteLine("5 + 3 = " + (5 + 3));
Console.WriteLine("5 - 3 = " + (5 - 3));
Console.WriteLine("5 * 3 = " + (5 * 3));
Console.WriteLine("5 / 3 = " + (5 / 3));
Console.WriteLine("5.2 % 3 = " + (5.2 % 3));
int i = 0;
Console.WriteLine("i++ = " + (i++));
Console.WriteLine("++i = " + (++i));
Console.WriteLine("i-- = " + (i--));
Console.WriteLine("--i = " + (--i));
Console.WriteLine("i +- 3 = " + (i +- 3));
Console.WriteLine("i -= 2 = " + (i -= 2));
Console.WriteLine("i *= 2 = " + (i *= 2));
Console.WriteLine("i /= 2 = " + (i /= 2));
Console.WriteLine("i %= 2 = " + (i %= 2));
// casting
// if no magnitude is lost, casting will happen automatically. But otherwise, you set it up as follows
double pi = 3.14;
int intPi = (int)pi;
Console.WriteLine("intPi = " + intPi);
// Math functions
// Acos, Asin, Atan, Atan2, Cos, Cosh, Exp, Log, Sin, Sinh, Tan, Tanh
double number1 = 10.5;
double number2 = 15;
Console.WriteLine("number1 is " + number1);
Console.WriteLine("number2 is " + number2);
Console.WriteLine("Math.Abs(number1) " + (Math.Abs(number1)));
Console.WriteLine("Math.Ceiling(number2) " + (Math.Ceiling(number1)));
Console.WriteLine("Math.Floor(number1) " + (Math.Floor(number1)));
Console.WriteLine("Math.Max(number1,number2) " + (Math.Max(number1,number2)));
Console.WriteLine("Math.Min(number1,number2) " + (Math.Min(number1,number2)));
Console.WriteLine("Math.Pow(number1, 2) " + (Math.Pow(number1, 2)));
Console.WriteLine("Math.Round(number1) " + (Math.Round(number1)));
Console.WriteLine("Math.Sqrt(number1) " + (Math.Sqrt(number1)));
// random numbers
Random rand = new Random();
Console.WriteLine("Random number between 1 and 10 is " + rand.Next(1, 11));
// Relational operators : > < >= <= == !=
// Logical operators : && || ^ !
// note: ^ is the exclusive or
Console.WriteLine("What is your child's age? (enter 0 - 18)");
int age = Console.Read();
if ((age >= 5) && (age <= 7))
{
Console.WriteLine("Go to Elementary School");
} else if ((age > 7) && (age <= 13))
{
Console.WriteLine("Go to middle school");
} else if ((age < 5) || (age > 13))
{
Console.WriteLine("Your child does not meet our age requirements.");
} else
{
Console.WriteLine("Go to high school");
}
Console.WriteLine("What is your age? ");
int workingAge = Console.Read();
if ((workingAge < 14) || (workingAge > 67))
{
Console.WriteLine("You shouldn't work.");
}
}
The program ignores the input from the following:
Console.WriteLine("What is your age? ");
int workingAge = Console.Read();
The output is:
What is your age?
You shouldn't work.
So, the program is not stopping for my input, but rather seems to process its conditions based on the previous integer input value of 2 or 5.
Other articles talked about doing the following which I tried with no avail:
Console.WriteLine("What is your age? ");
int workingAge = Convert.ToInt32(Console.Read());
And
Console.WriteLine("What is your age? ");
int workingAge = int32.Parse(Console.Read());
The second one produced an error in Visual Studio The name 'int32' does not exist in the current context
I updated the script to use int.Parse(Console.ReadLine()), and it worked on Visual Studio 2007, but I ran this on Visual Studio 2015 Community Edition and it is doing the same exact thing as if the changes had no effect:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
// Single line comments
/* test multi-line comments
* asldkjasldkjaskd
* asldkjasldkja
* alsdkjalksdj
* */
Console.WriteLine("Hello world!");
Console.Write("What is your name? ");
string name = Console.ReadLine();
Console.WriteLine("Hello " + name);
bool canVote = true;
char grade = 'A';
// Integer with a max number of 2,147,483,647
int maxInt = int.MaxValue;
//Long with max value of 9,223,372,036,854,775,807
long maxLong = long.MaxValue;
// Decimal has a max value of 79,228,162,514,264,337,593,543,950,335
// If you need something bigger, look up BigInteger
decimal maxDecimal = decimal.MaxValue;
// A float is a 32 bit number with a max value of 3.402823E+38 with 7 decimal positions
float maxFloat = float.MaxValue;
// A double is a 32 bit number with a max value of 1.797693134E+308 with 15 decimal positions
double maxDouble = double.MaxValue;
Console.WriteLine("Max Int : " + maxInt);
Console.WriteLine("Max Long : " + maxLong);
Console.WriteLine("Max Decimal : " + maxDecimal);
Console.WriteLine("Max Float : " + maxFloat);
Console.WriteLine("Max Double : " + maxDouble);
var anotherName = "Tom";
// anotherName = 2; Cannot implicitly convert a gype 'int' to a 'string'
Console.WriteLine("anotherName is a {0}", anotherName.GetTypeCode());
// Math
Console.WriteLine("5 + 3 = " + (5 + 3));
Console.WriteLine("5 - 3 = " + (5 - 3));
Console.WriteLine("5 * 3 = " + (5 * 3));
Console.WriteLine("5 / 3 = " + (5 / 3));
Console.WriteLine("5.2 % 3 = " + (5.2 % 3));
int i = 0;
Console.WriteLine("i++ = " + (i++));
Console.WriteLine("++i = " + (++i));
Console.WriteLine("i-- = " + (i--));
Console.WriteLine("--i = " + (--i));
Console.WriteLine("i +- 3 = " + (i + -3));
Console.WriteLine("i -= 2 = " + (i -= 2));
Console.WriteLine("i *= 2 = " + (i *= 2));
Console.WriteLine("i /= 2 = " + (i /= 2));
Console.WriteLine("i %= 2 = " + (i %= 2));
// casting
// if no magnitude is lost, casting will happen automatically. But otherwise, you set it up as follows
double pi = 3.14;
int intPi = (int)pi;
Console.WriteLine("intPi = " + intPi);
// Math functions
// Acos, Asin, Atan, Atan2, Cos, Cosh, Exp, Log, Sin, Sinh, Tan, Tanh
double number1 = 10.5;
double number2 = 15;
Console.WriteLine("number1 is " + number1);
Console.WriteLine("number2 is " + number2);
Console.WriteLine("Math.Abs(number1) " + (Math.Abs(number1)));
Console.WriteLine("Math.Ceiling(number2) " + (Math.Ceiling(number1)));
Console.WriteLine("Math.Floor(number1) " + (Math.Floor(number1)));
Console.WriteLine("Math.Max(number1,number2) " + (Math.Max(number1, number2)));
Console.WriteLine("Math.Min(number1,number2) " + (Math.Min(number1, number2)));
Console.WriteLine("Math.Pow(number1, 2) " + (Math.Pow(number1, 2)));
Console.WriteLine("Math.Round(number1) " + (Math.Round(number1)));
Console.WriteLine("Math.Sqrt(number1) " + (Math.Sqrt(number1)));
// random numbers
Random rand = new Random();
Console.WriteLine("Random number between 1 and 10 is " + rand.Next(1, 11));
// Relational operators : > < >= <= == !=
// Logical operators : && || ^ !
// note: ^ is the exclusive or
Console.WriteLine("What is your child's age? (enter 0 - 18)");
int age = int.Parse(Console.ReadLine());
if ((age >= 5) && (age <= 7))
{
Console.WriteLine("Go to Elementary School");
}
else if ((age > 7) && (age <= 13))
{
Console.WriteLine("Go to middle school");
}
else if ((age < 4) || (age > 18))
{
Console.WriteLine("Your child does not meet our age requirements.");
}
else
{
Console.WriteLine("Go to high school");
}
Console.WriteLine("What is your age? ");
int workingAge = int.Parse(Console.ReadLine());
if ((workingAge < 14) || (workingAge > 67))
{
Console.WriteLine("You shouldn't work.");
}
else
{
Console.WriteLine("Work harder and smarter to get ahead.");
}
}
}
}
Please help.

.Read() reads only a single character. You probably want .ReadLine() instead, which reads all the characters up to Enter, and returns a string.
int workingAge = int.Parse(Console.ReadLine());

Expanding off of #recursive you can use int32.TryParse() to check if a valid number was supplied.
bool valid = false;
int workingAge;
while (!valid)
{
valid = int32.TryParse(Console.ReadLine(), out workingAge);
if (!valid)
Console.WriteLine("Supplied number was invalid");
}
// Rest of code
Edit: I think this can be simplified even further by doing the following:
int workingAge;
while (!int32.TryParse(Console.ReadLine(), out workingAge))
{
Console.WriteLine("Supplied number was invalid");
}
// Rest of code

I will add to recursive's solution and explain what is happening.
since you are using Console.Read() in two different areas -
and since Console.Read() reads one key input (i.e '1') -
you are probably entering two different digits in the first occurance which causes the first .Read() to only read the first digit, and "passes" the second digit to the second .Read()
as was said before me, changing the .Read() to .ReadLine() will solve your issue.

How can remove the last digit in an int (C#)?

How can I remove the last digit in an int (C#)?
I would like to use in c# console, user put 9 digit number and I remove the last digit of number
how should I choose some digit from above for example 1234456782 and i choose 2-4-6-8?

You should try to divide it by 10:
int number = 123456789;
int newNumber= number/10;
Console.WriteLine("new number: {0}", newNumber);

int i = 123456789
int newVal = i/10;

1.
string num = input.ToString();
if (num.Length > 1)
{
num = num.Remove(num.Length - 1, 1);
}
2.
num = num[1] + num[4] + num[6] + num[8];

num -= num % 10;

int num = 123456;
int numMinusUnitsDigit = 10 * (num / 10);
Console.WriteLine("number without Units digit: {0}", numMinusUnitsDigit );

How to convert a column number (e.g. 127) into an Excel column (e.g. AA)

How do you convert a numerical number to an Excel column name in C# without using automation getting the value directly from Excel.
Excel 2007 has a possible range of 1 to 16384, which is the number of columns that it supports. The resulting values should be in the form of excel column names, e.g. A, AA, AAA etc.

Here's how I do it:
private string GetExcelColumnName(int columnNumber)
{
string columnName = "";
while (columnNumber > 0)
{
int modulo = (columnNumber - 1) % 26;
columnName = Convert.ToChar('A' + modulo) + columnName;
columnNumber = (columnNumber - modulo) / 26;
}
return columnName;
}

If anyone needs to do this in Excel without VBA, here is a way:
=SUBSTITUTE(ADDRESS(1;colNum;4);"1";"")
where colNum is the column number
And in VBA:
Function GetColumnName(colNum As Integer) As String
Dim d As Integer
Dim m As Integer
Dim name As String
d = colNum
name = ""
Do While (d > 0)
m = (d - 1) Mod 26
name = Chr(65 + m) + name
d = Int((d - m) / 26)
Loop
GetColumnName = name
End Function

You might need conversion both ways, e.g from Excel column adress like AAZ to integer and from any integer to Excel. The two methods below will do just that. Assumes 1 based indexing, first element in your "arrays" are element number 1.
No limits on size here, so you can use adresses like ERROR and that would be column number 2613824 ...
public static string ColumnAdress(int col)
{
if (col <= 26) {
return Convert.ToChar(col + 64).ToString();
}
int div = col / 26;
int mod = col % 26;
if (mod == 0) {mod = 26;div--;}
return ColumnAdress(div) + ColumnAdress(mod);
}
public static int ColumnNumber(string colAdress)
{
int[] digits = new int[colAdress.Length];
for (int i = 0; i < colAdress.Length; ++i)
{
digits[i] = Convert.ToInt32(colAdress[i]) - 64;
}
int mul=1;int res=0;
for (int pos = digits.Length - 1; pos >= 0; --pos)
{
res += digits[pos] * mul;
mul *= 26;
}
return res;
}

Sorry, this is Python instead of C#, but at least the results are correct:
def ColIdxToXlName(idx):
if idx < 1:
raise ValueError("Index is too small")
result = ""
while True:
if idx > 26:
idx, r = divmod(idx - 1, 26)
result = chr(r + ord('A')) + result
else:
return chr(idx + ord('A') - 1) + result
for i in xrange(1, 1024):
print "%4d : %s" % (i, ColIdxToXlName(i))

I discovered an error in my first post, so I decided to sit down and do the the math. What I found is that the number system used to identify Excel columns is not a base 26 system, as another person posted. Consider the following in base 10. You can also do this with the letters of the alphabet.
Space:.........................S1, S2, S3 : S1, S2, S3
....................................0, 00, 000 :.. A, AA, AAA
....................................1, 01, 001 :.. B, AB, AAB
.................................... …, …, … :.. …, …, …
....................................9, 99, 999 :.. Z, ZZ, ZZZ
Total states in space: 10, 100, 1000 : 26, 676, 17576
Total States:...............1110................18278
Excel numbers columns in the individual alphabetical spaces using base 26. You can see that in general, the state space progression is a, a^2, a^3, … for some base a, and the total number of states is a + a^2 + a^3 + … .
Suppose you want to find the total number of states A in the first N spaces. The formula for doing so is A = (a)(a^N - 1 )/(a-1). This is important because we need to find the space N that corresponds to our index K. If I want to find out where K lies in the number system I need to replace A with K and solve for N. The solution is N = log{base a} (A (a-1)/a +1). If I use the example of a = 10 and K = 192, I know that N = 2.23804… . This tells me that K lies at the beginning of the third space since it is a little greater than two.
The next step is to find exactly how far in the current space we are. To find this, subtract from K the A generated using the floor of N. In this example, the floor of N is two. So, A = (10)(10^2 – 1)/(10-1) = 110, as is expected when you combine the states of the first two spaces. This needs to be subtracted from K because these first 110 states would have already been accounted for in the first two spaces. This leaves us with 82 states. So, in this number system, the representation of 192 in base 10 is 082.
The C# code using a base index of zero is
private string ExcelColumnIndexToName(int Index)
{
string range = string.Empty;
if (Index < 0 ) return range;
int a = 26;
int x = (int)Math.Floor(Math.Log((Index) * (a - 1) / a + 1, a));
Index -= (int)(Math.Pow(a, x) - 1) * a / (a - 1);
for (int i = x+1; Index + i > 0; i--)
{
range = ((char)(65 + Index % a)).ToString() + range;
Index /= a;
}
return range;
}
//Old Post
A zero-based solution in C#.
private string ExcelColumnIndexToName(int Index)
{
string range = "";
if (Index < 0 ) return range;
for(int i=1;Index + i > 0;i=0)
{
range = ((char)(65 + Index % 26)).ToString() + range;
Index /= 26;
}
if (range.Length > 1) range = ((char)((int)range[0] - 1)).ToString() + range.Substring(1);
return range;
}

This answer is in javaScript:
function getCharFromNumber(columnNumber){
var dividend = columnNumber;
var columnName = "";
var modulo;
while (dividend > 0)
{
modulo = (dividend - 1) % 26;
columnName = String.fromCharCode(65 + modulo).toString() + columnName;
dividend = parseInt((dividend - modulo) / 26);
}
return columnName;
}

Easy with recursion.
public static string GetStandardExcelColumnName(int columnNumberOneBased)
{
int baseValue = Convert.ToInt32('A');
int columnNumberZeroBased = columnNumberOneBased - 1;
string ret = "";
if (columnNumberOneBased > 26)
{
ret = GetStandardExcelColumnName(columnNumberZeroBased / 26) ;
}
return ret + Convert.ToChar(baseValue + (columnNumberZeroBased % 26) );
}

I'm surprised all of the solutions so far contain either iteration or recursion.
Here's my solution that runs in constant time (no loops). This solution works for all possible Excel columns and checks that the input can be turned into an Excel column. Possible columns are in the range [A, XFD] or [1, 16384]. (This is dependent on your version of Excel)
private static string Turn(uint col)
{
if (col < 1 || col > 16384) //Excel columns are one-based (one = 'A')
throw new ArgumentException("col must be >= 1 and <= 16384");
if (col <= 26) //one character
return ((char)(col + 'A' - 1)).ToString();
else if (col <= 702) //two characters
{
char firstChar = (char)((int)((col - 1) / 26) + 'A' - 1);
char secondChar = (char)(col % 26 + 'A' - 1);
if (secondChar == '#') //Excel is one-based, but modulo operations are zero-based
secondChar = 'Z'; //convert one-based to zero-based
return string.Format("{0}{1}", firstChar, secondChar);
}
else //three characters
{
char firstChar = (char)((int)((col - 1) / 702) + 'A' - 1);
char secondChar = (char)((col - 1) / 26 % 26 + 'A' - 1);
char thirdChar = (char)(col % 26 + 'A' - 1);
if (thirdChar == '#') //Excel is one-based, but modulo operations are zero-based
thirdChar = 'Z'; //convert one-based to zero-based
return string.Format("{0}{1}{2}", firstChar, secondChar, thirdChar);
}
}

Same implementation in Java
public String getExcelColumnName (int columnNumber)
{
int dividend = columnNumber;
int i;
String columnName = "";
int modulo;
while (dividend > 0)
{
modulo = (dividend - 1) % 26;
i = 65 + modulo;
columnName = new Character((char)i).toString() + columnName;
dividend = (int)((dividend - modulo) / 26);
}
return columnName;
}

int nCol = 127;
string sChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string sCol = "";
while (nCol >= 26)
{
int nChar = nCol % 26;
nCol = (nCol - nChar) / 26;
// You could do some trick with using nChar as offset from 'A', but I am lazy to do it right now.
sCol = sChars[nChar] + sCol;
}
sCol = sChars[nCol] + sCol;
Update: Peter's comment is right. That's what I get for writing code in the browser. :-) My solution was not compiling, it was missing the left-most letter and it was building the string in reverse order - all now fixed.
Bugs aside, the algorithm is basically converting a number from base 10 to base 26.
Update 2: Joel Coehoorn is right - the code above will return AB for 27. If it was real base 26 number, AA would be equal to A and the next number after Z would be BA.
int nCol = 127;
string sChars = "0ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string sCol = "";
while (nCol > 26)
{
int nChar = nCol % 26;
if (nChar == 0)
nChar = 26;
nCol = (nCol - nChar) / 26;
sCol = sChars[nChar] + sCol;
}
if (nCol != 0)
sCol = sChars[nCol] + sCol;

..And converted to php:
function GetExcelColumnName($columnNumber) {
$columnName = '';
while ($columnNumber > 0) {
$modulo = ($columnNumber - 1) % 26;
$columnName = chr(65 + $modulo) . $columnName;
$columnNumber = (int)(($columnNumber - $modulo) / 26);
}
return $columnName;
}

Just throwing in a simple two-line C# implementation using recursion, because all the answers here seem far more complicated than necessary.
/// <summary>
/// Gets the column letter(s) corresponding to the given column number.
/// </summary>
/// <param name="column">The one-based column index. Must be greater than zero.</param>
/// <returns>The desired column letter, or an empty string if the column number was invalid.</returns>
public static string GetColumnLetter(int column) {
if (column < 1) return String.Empty;
return GetColumnLetter((column - 1) / 26) + (char)('A' + (column - 1) % 26);
}

Although there are already a bunch of valid answers1, none get into the theory behind it.
Excel column names are bijective base-26 representations of their number. This is quite different than an ordinary base 26 (there is no leading zero), and I really recommend reading the Wikipedia entry to grasp the differences. For example, the decimal value 702 (decomposed in 26*26 + 26) is represented in "ordinary" base 26 by 110 (i.e. 1x26^2 + 1x26^1 + 0x26^0) and in bijective base-26 by ZZ (i.e. 26x26^1 + 26x26^0).
Differences aside, bijective numeration is a positional notation, and as such we can perform conversions using an iterative (or recursive) algorithm which on each iteration finds the digit of the next position (similarly to an ordinary base conversion algorithm).
The general formula to get the digit at the last position (the one indexed 0) of the bijective base-k representation of a decimal number m is (f being the ceiling function minus 1):
m - (f(m / k) * k)
The digit at the next position (i.e. the one indexed 1) is found by applying the same formula to the result of f(m / k). We know that for the last digit (i.e. the one with the highest index) f(m / k) is 0.
This forms the basis for an iteration that finds each successive digit in bijective base-k of a decimal number. In pseudo-code it would look like this (digit() maps a decimal integer to its representation in the bijective base -- e.g. digit(1) would return A in bijective base-26):
fun conv(m)
q = f(m / k)
a = m - (q * k)
if (q == 0)
return digit(a)
else
return conv(q) + digit(a);
So we can translate this to C#2 to get a generic3 "conversion to bijective base-k" ToBijective() routine:
class BijectiveNumeration {
private int baseK;
private Func<int, char> getDigit;
public BijectiveNumeration(int baseK, Func<int, char> getDigit) {
this.baseK = baseK;
this.getDigit = getDigit;
}
public string ToBijective(double decimalValue) {
double q = f(decimalValue / baseK);
double a = decimalValue - (q * baseK);
return ((q > 0) ? ToBijective(q) : "") + getDigit((int)a);
}
private static double f(double i) {
return (Math.Ceiling(i) - 1);
}
}
Now for conversion to bijective base-26 (our "Excel column name" use case):
static void Main(string[] args)
{
BijectiveNumeration bijBase26 = new BijectiveNumeration(
26,
(value) => Convert.ToChar('A' + (value - 1))
);
Console.WriteLine(bijBase26.ToBijective(1)); // prints "A"
Console.WriteLine(bijBase26.ToBijective(26)); // prints "Z"
Console.WriteLine(bijBase26.ToBijective(27)); // prints "AA"
Console.WriteLine(bijBase26.ToBijective(702)); // prints "ZZ"
Console.WriteLine(bijBase26.ToBijective(16384)); // prints "XFD"
}
Excel's maximum column index is 16384 / XFD, but this code will convert any positive number.
As an added bonus, we can now easily convert to any bijective base. For example for bijective base-10:
static void Main(string[] args)
{
BijectiveNumeration bijBase10 = new BijectiveNumeration(
10,
(value) => value < 10 ? Convert.ToChar('0'+value) : 'A'
);
Console.WriteLine(bijBase10.ToBijective(1)); // prints "1"
Console.WriteLine(bijBase10.ToBijective(10)); // prints "A"
Console.WriteLine(bijBase10.ToBijective(123)); // prints "123"
Console.WriteLine(bijBase10.ToBijective(20)); // prints "1A"
Console.WriteLine(bijBase10.ToBijective(100)); // prints "9A"
Console.WriteLine(bijBase10.ToBijective(101)); // prints "A1"
Console.WriteLine(bijBase10.ToBijective(2010)); // prints "19AA"
}
1 This generic answer can eventually be reduced to the other, correct, specific answers, but I find it hard to fully grasp the logic of the solutions without the formal theory behind bijective numeration in general. It also proves its correctness nicely. Additionally, several similar questions link back to this one, some being language-agnostic or more generic. That's why I thought the addition of this answer was warranted, and that this question was a good place to put it.
2 C# disclaimer: I implemented an example in C# because this is what is asked here, but I have never learned nor used the language. I have verified it does compile and run, but please adapt it to fit the language best practices / general conventions, if necessary.
3 This example only aims to be correct and understandable ; it could and should be optimized would performance matter (e.g. with tail-recursion -- but that seems to require trampolining in C#), and made safer (e.g. by validating parameters).

I wanted to throw in my static class I use, for interoping between col index and col Label. I use a modified accepted answer for my ColumnLabel Method
public static class Extensions
{
public static string ColumnLabel(this int col)
{
var dividend = col;
var columnLabel = string.Empty;
int modulo;
while (dividend > 0)
{
modulo = (dividend - 1) % 26;
columnLabel = Convert.ToChar(65 + modulo).ToString() + columnLabel;
dividend = (int)((dividend - modulo) / 26);
}
return columnLabel;
}
public static int ColumnIndex(this string colLabel)
{
// "AD" (1 * 26^1) + (4 * 26^0) ...
var colIndex = 0;
for(int ind = 0, pow = colLabel.Count()-1; ind < colLabel.Count(); ++ind, --pow)
{
var cVal = Convert.ToInt32(colLabel[ind]) - 64; //col A is index 1
colIndex += cVal * ((int)Math.Pow(26, pow));
}
return colIndex;
}
}
Use this like...
30.ColumnLabel(); // "AD"
"AD".ColumnIndex(); // 30

private String getColumn(int c) {
String s = "";
do {
s = (char)('A' + (c % 26)) + s;
c /= 26;
} while (c-- > 0);
return s;
}
Its not exactly base 26, there is no 0 in the system. If there was, 'Z' would be followed by 'BA' not by 'AA'.

if you just want it for a cell formula without code, here's a formula for it:
IF(COLUMN()>=26,CHAR(ROUND(COLUMN()/26,1)+64)&CHAR(MOD(COLUMN(),26)+64),CHAR(COLUMN()+64))

In Delphi (Pascal):
function GetExcelColumnName(columnNumber: integer): string;
var
dividend, modulo: integer;
begin
Result := '';
dividend := columnNumber;
while dividend > 0 do begin
modulo := (dividend - 1) mod 26;
Result := Chr(65 + modulo) + Result;
dividend := (dividend - modulo) div 26;
end;
end;

A little late to the game, but here's the code I use (in C#):
private static readonly string _Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static int ColumnNameParse(string value)
{
// assumes value.Length is [1,3]
// assumes value is uppercase
var digits = value.PadLeft(3).Select(x => _Alphabet.IndexOf(x));
return digits.Aggregate(0, (current, index) => (current * 26) + (index + 1));
}

In perl, for an input of 1 (A), 27 (AA), etc.
sub excel_colname {
my ($idx) = #_; # one-based column number
--$idx; # zero-based column index
my $name = "";
while ($idx >= 0) {
$name .= chr(ord("A") + ($idx % 26));
$idx = int($idx / 26) - 1;
}
return scalar reverse $name;
}

Though I am late to the game, Graham's answer is far from being optimal. Particularly, you don't have to use the modulo, call ToString() and apply (int) cast. Considering that in most cases in C# world you would start numbering from 0, here is my revision:
public static string GetColumnName(int index) // zero-based
{
const byte BASE = 'Z' - 'A' + 1;
string name = String.Empty;
do
{
name = Convert.ToChar('A' + index % BASE) + name;
index = index / BASE - 1;
}
while (index >= 0);
return name;
}

More than 30 solutions already, but here's my one-line C# solution...
public string IntToExcelColumn(int i)
{
return ((i<16926? "" : ((char)((((i/26)-1)%26)+65)).ToString()) + (i<2730? "" : ((char)((((i/26)-1)%26)+65)).ToString()) + (i<26? "" : ((char)((((i/26)-1)%26)+65)).ToString()) + ((char)((i%26)+65)));
}

After looking at all the supplied Versions here, I decided to do one myself, using recursion.
Here is my vb.net Version:
Function CL(ByVal x As Integer) As String
If x >= 1 And x <= 26 Then
CL = Chr(x + 64)
Else
CL = CL((x - x Mod 26) / 26) & Chr((x Mod 26) + 1 + 64)
End If
End Function

Refining the original solution (in C#):
public static class ExcelHelper
{
private static Dictionary<UInt16, String> l_DictionaryOfColumns;
public static ExcelHelper() {
l_DictionaryOfColumns = new Dictionary<ushort, string>(256);
}
public static String GetExcelColumnName(UInt16 l_Column)
{
UInt16 l_ColumnCopy = l_Column;
String l_Chars = "0ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String l_rVal = "";
UInt16 l_Char;
if (l_DictionaryOfColumns.ContainsKey(l_Column) == true)
{
l_rVal = l_DictionaryOfColumns[l_Column];
}
else
{
while (l_ColumnCopy > 26)
{
l_Char = l_ColumnCopy % 26;
if (l_Char == 0)
l_Char = 26;
l_ColumnCopy = (l_ColumnCopy - l_Char) / 26;
l_rVal = l_Chars[l_Char] + l_rVal;
}
if (l_ColumnCopy != 0)
l_rVal = l_Chars[l_ColumnCopy] + l_rVal;
l_DictionaryOfColumns.ContainsKey(l_Column) = l_rVal;
}
return l_rVal;
}
}

Here is an Actionscript version:
private var columnNumbers:Array = ['A', 'B', 'C', 'D', 'E', 'F' , 'G', 'H', 'I', 'J', 'K' ,'L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
private function getExcelColumnName(columnNumber:int) : String{
var dividend:int = columnNumber;
var columnName:String = "";
var modulo:int;
while (dividend > 0)
{
modulo = (dividend - 1) % 26;
columnName = columnNumbers[modulo] + columnName;
dividend = int((dividend - modulo) / 26);
}
return columnName;
}

JavaScript Solution
/**
* Calculate the column letter abbreviation from a 1 based index
* #param {Number} value
* #returns {string}
*/
getColumnFromIndex = function (value) {
var base = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('');
var remainder, result = "";
do {
remainder = value % 26;
result = base[(remainder || 26) - 1] + result;
value = Math.floor(value / 26);
} while (value > 0);
return result;
};

These my codes to convert specific number (index start from 1) to Excel Column.
public static string NumberToExcelColumn(uint number)
{
uint originalNumber = number;
uint numChars = 1;
while (Math.Pow(26, numChars) < number)
{
numChars++;
if (Math.Pow(26, numChars) + 26 >= number)
{
break;
}
}
string toRet = "";
uint lastValue = 0;
do
{
number -= lastValue;
double powerVal = Math.Pow(26, numChars - 1);
byte thisCharIdx = (byte)Math.Truncate((columnNumber - 1) / powerVal);
lastValue = (int)powerVal * thisCharIdx;
if (numChars - 2 >= 0)
{
double powerVal_next = Math.Pow(26, numChars - 2);
byte thisCharIdx_next = (byte)Math.Truncate((columnNumber - lastValue - 1) / powerVal_next);
int lastValue_next = (int)Math.Pow(26, numChars - 2) * thisCharIdx_next;
if (thisCharIdx_next == 0 && lastValue_next == 0 && powerVal_next == 26)
{
thisCharIdx--;
lastValue = (int)powerVal * thisCharIdx;
}
}
toRet += (char)((byte)'A' + thisCharIdx + ((numChars > 1) ? -1 : 0));
numChars--;
} while (numChars > 0);
return toRet;
}
My Unit Test:
[TestMethod]
public void Test()
{
Assert.AreEqual("A", NumberToExcelColumn(1));
Assert.AreEqual("Z", NumberToExcelColumn(26));
Assert.AreEqual("AA", NumberToExcelColumn(27));
Assert.AreEqual("AO", NumberToExcelColumn(41));
Assert.AreEqual("AZ", NumberToExcelColumn(52));
Assert.AreEqual("BA", NumberToExcelColumn(53));
Assert.AreEqual("ZZ", NumberToExcelColumn(702));
Assert.AreEqual("AAA", NumberToExcelColumn(703));
Assert.AreEqual("ABC", NumberToExcelColumn(731));
Assert.AreEqual("ACQ", NumberToExcelColumn(771));
Assert.AreEqual("AYZ", NumberToExcelColumn(1352));
Assert.AreEqual("AZA", NumberToExcelColumn(1353));
Assert.AreEqual("AZB", NumberToExcelColumn(1354));
Assert.AreEqual("BAA", NumberToExcelColumn(1379));
Assert.AreEqual("CNU", NumberToExcelColumn(2413));
Assert.AreEqual("GCM", NumberToExcelColumn(4823));
Assert.AreEqual("MSR", NumberToExcelColumn(9300));
Assert.AreEqual("OMB", NumberToExcelColumn(10480));
Assert.AreEqual("ULV", NumberToExcelColumn(14530));
Assert.AreEqual("XFD", NumberToExcelColumn(16384));
}

Sorry, this is Python instead of C#, but at least the results are correct:
def excel_column_number_to_name(column_number):
output = ""
index = column_number-1
while index >= 0:
character = chr((index%26)+ord('A'))
output = output + character
index = index/26 - 1
return output[::-1]
for i in xrange(1, 1024):
print "%4d : %s" % (i, excel_column_number_to_name(i))
Passed these test cases:
Column Number: 494286 => ABCDZ
Column Number: 27 => AA
Column Number: 52 => AZ

For what it is worth, here is Graham's code in Powershell:
function ConvertTo-ExcelColumnID {
param (
[parameter(Position = 0,
HelpMessage = "A 1-based index to convert to an excel column ID. e.g. 2 => 'B', 29 => 'AC'",
Mandatory = $true)]
[int]$index
);
[string]$result = '';
if ($index -le 0 ) {
return $result;
}
while ($index -gt 0) {
[int]$modulo = ($index - 1) % 26;
$character = [char]($modulo + [int][char]'A');
$result = $character + $result;
[int]$index = ($index - $modulo) / 26;
}
return $result;
}

Another VBA way
Public Function GetColumnName(TargetCell As Range) As String
GetColumnName = Split(CStr(TargetCell.Cells(1, 1).Address), "$")(1)
End Function

Here's my super late implementation in PHP. This one's recursive. I wrote it just before I found this post. I wanted to see if others had solved this problem already...
public function GetColumn($intNumber, $strCol = null) {
if ($intNumber > 0) {
$intRem = ($intNumber - 1) % 26;
$strCol = $this->GetColumn(intval(($intNumber - $intRem) / 26), sprintf('%s%s', chr(65 + $intRem), $strCol));
}
return $strCol;
}