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Take only letters from the string and reverse them

I'm preparing for my interview, faced the problem with the task. The case is that we're having a string:
test12pop90java989python
I need to return new string where words will be reversed and numbers will stay in the same place:
test12pop90java989python ==> tset12pop90avaj989nohtyp
What I started with:
Transferring string to char array
Use for loop + Char.IsNumber
??
var charArray = test.ToCharArray();
for (int i = 0; i < charArray.Length; i++)
{
if (!Char.IsNumber(charArray[i]))
{
....
}
}
but currently I'm stuck and don't know how to proceed, any tips how it can be done?

You can't reverse a run of letters until you've observed the entire run; until then, you need to keep track of the pending letters to be reversed and appended to the final output upon encountering a number or the end of the string. By storing these pending characters in a Stack<> they are naturally returned in the reverse order they were added.
static string Transform(string input)
{
StringBuilder outputBuilder = new StringBuilder(input.Length);
Stack<char> pending = new Stack<char>();
foreach (char c in input)
if (char.IsNumber(c))
{
// In the reverse order of which they were added, consume
// and append pending characters as long as they are available
while (pending.Count > 0)
outputBuilder.Append(pending.Pop());
// Alternatively...
//foreach (char p in pending)
// outputBuilder.Append(p);
//pending.Clear();
outputBuilder.Append(c);
}
else
pending.Push(c);
// Handle pending characters when input does not end with a number
while (pending.Count > 0)
outputBuilder.Append(pending.Pop());
return outputBuilder.ToString();
}
A similar but buffer-free way is to do it is to store the index of the start of the current run of letters, then walk back through and append each character when a number is found...
static string Transform(string input)
{
StringBuilder outputBuilder = new StringBuilder(input.Length);
int lettersStartIndex = -1;
for (int i = 0; i < input.Length; i++)
{
char c = input[i];
if (char.IsNumber(c))
{
if (lettersStartIndex >= 0)
{
// Iterate backwards from the previous character to the start of the run
for (int j = i - 1; j >= lettersStartIndex; j--)
outputBuilder.Append(input[j]);
lettersStartIndex = -1;
}
outputBuilder.Append(c);
}
else if (lettersStartIndex < 0)
lettersStartIndex = i;
}
// Handle remaining characters when input does not end with a number
if (lettersStartIndex >= 0)
for (int j = input.Length - 1; j >= lettersStartIndex; j--)
outputBuilder.Append(input[j]);
return outputBuilder.ToString();
}
For both implementations, calling Transform() with...
string[] inputs = new string[] {
"test12pop90java989python",
"123test12pop90java989python321",
"This text contains no numbers",
"1a2b3c"
};
for (int i = 0; i < inputs.Length; i++)
{
string input = inputs[i];
string output = Transform(input);
Console.WriteLine($" Input[{i}]: \"{input }\"");
Console.WriteLine($"Output[{i}]: \"{output}\"");
Console.WriteLine();
}
...produces this output...
Input[0]: "test12pop90java989python"
Output[0]: "tset12pop90avaj989nohtyp"
Input[1]: "123test12pop90java989python321"
Output[1]: "123tset12pop90avaj989nohtyp321"
Input[2]: "This text contains no numbers"
Output[2]: "srebmun on sniatnoc txet sihT"
Input[3]: "1a2b3c"
Output[3]: "1a2b3c"

A possible solution using Regex and Linq:
using System;
using System.Text.RegularExpressions;
using System.Linq;
public class Program
{
public static void Main()
{
var result = "";
var matchList = Regex.Matches("test12pop90java989python", "([a-zA-Z]*)(\\d*)");
var list = matchList.Cast<Match>().SelectMany(o =>o.Groups.Cast<Capture>().Skip(1).Select(c => c.Value));
foreach (var el in list)
{
if (el.All(char.IsDigit))
{
result += el;
}
else
{
result += new string(el.Reverse().ToArray());
}
}
Console.WriteLine(result);
}
}
I've used code from stackoverflow.com/a/21123574/1037948 to create a list of Regex matches on line 11:
var list = matchList.Cast<Match>().SelectMany(o =>o.Groups.Cast<Capture>().Skip(1).Select(c => c.Value));

Hey you can do something like:
string test = "test12pop90java989python", tempStr = "", finalstr = "";
var charArray = test.ToCharArray();
for (int i = 0; i < charArray.Length; i++)
{
if (!Char.IsNumber(charArray[i]))
{
tempStr += charArray[i];
}
else
{
char[] ReverseString = tempStr.Reverse().ToArray();
foreach (char charItem in ReverseString)
{
finalstr += charItem;
}
tempStr = "";
finalstr += charArray[i];
}
}
if(tempStr != "" && tempStr != null)
{
char[] ReverseString = tempStr.Reverse().ToArray();
foreach (char charItem in ReverseString)
{
finalstr += charItem;
}
tempStr = "";
}
I hope this helps

I am unable to use substring. How can I fix this?

I am trying to see weather the string is in alphabetical order or no and this error pops up
System.ArgumentOutOfRangeException: Index and length must refer to a location within the string.
Parameter name: length
at System.String.Substring(Int32 startIndex, Int32 length)
at Rextester.Program.Main(String[] args)**
public static void Main(string[] args)
{
string str = "bat\ncat\ndog\n";
int c = 0;
for (int i = 0; i < str.Length; i++)
{
if ((str.Substring(i,i + 1).Equals("\n")))
{
c++;
}
}
String[] strArray = new String[c + 1]; //declare with size
int g = 0;
String h = "";
for (int i = 0; i < str.Length; i++)
{
if ((str.Substring(i,i + 1).Equals("\n")))
{
strArray[g] = h;
h = "";
g = g + 1;
}
else
{
h = h + str.Substring(i,i + 1);
}
}
String p = "True";
for (int i = 0; i < g; i++)
{
if (i < (g - 1))
{
String f = strArray[i];
String g2 = strArray[i + 1];
char d = f[0];
char s = g2[0];
int d1 = (int)d;
int s1 = (int)s;
if (d1 > s1)
{
p = "False";
}
}
}
Console.WriteLine(p);
}
}

Not sure about what you are doing in your second loop and why is it so complex. We can do the same like this. Hope this helps.
using System;
public class Program
{
public static void Main()
{
string str = "abcd";
str = str.Replace('\n',' ');
String p = "True";
for (int i = 1; i < str.Length; i++) {
// if element at index 'i' is less
// than the element at index 'i-1'
// then the string is not sorted
if (str[i] < str[i - 1]) {
p = "false";
}
}
Console.WriteLine(p);
}
}

Pay attention to the definition of substring
The substring starts at a specified character position and has a
specified length
Considering your first use of substring, here
for (int i = 0; i < str.Length; i++)
{
if (str.Substring(i, i + 1).Equals("\n"))
{
c++;
}
}
What happens when we get to i=6 here? Substring tries to give you a new string that starts at position i = 6, and is length = 7 characters long. So it tries to give you 7 characters starting from str[6] to str[12]. Well, there is no str[12], so you get an exception.
Its clear that your intent is NOT to get a string that starts at position 6 and is 7 characters long. You want ONE character, so your loop should be this
for (int i = 0; i < str.Length; i++)
{
if (str.Substring(i, 1).Equals("\n"))
{
c++;
}
}
But theres a much simpler way to get your words in alphabetical order using LINQ
string str = "bat\ncat\ndog\n";
//Removes the trailing \n so you don't have one entry that is only whitespace
str = str.Trim();
string[] strSplit = str.Split('\n').OrderBy(x => x[0]).ToArray();
Now all substrings are sorted alphabetically and you can do whatever you want with them

merge two strings based on index of character

I am trying to write a code to merge two string based on index of character.For e.g-If we have two string "abc" and "defg",I want a string output1(merging all even character of both strings)="adcf" and another string output2="beg" (remaining all words).
What I tried-
class Program
{
static void Main(string[] args)
{
string a= "First";
string b= "MiddleName";
string newstring = "";
string newstring1 = "";
int length = b.Length;
for (int l = 0; l < length; l=l+1)
{
if(l%2==0)
{
newstring = newstring + a[l].ToString() + b[l].ToString();
}
if (l % 2 == 1)
{
newstring1 = newstring1 + a[l].ToString() + b[l].ToString();
}
}
Console.ReadLine();
}
}
But then in this case it will give outside the bound array exception.Any better way to do this?
Thanks

I suggest extracting a method where you should solve the generalized problem of merging two strings taking each step characters from them starting from offset:
private static String Merge(String left, String right, int step, int offset) {
StringBuilder sb = new StringBuilder();
if (null == left)
left = ""; // or throw exception
if (null == right)
right = ""; // or throw exception
for (int i = offset; i < Math.Max(left.Length, right.Length); i += step) {
//DONE: do not forget to check if you can get a character
if (i < left.Length)
sb.Append(left[i]);
//DONE: do not forget to check if you can get a character
if (i < right.Length)
sb.Append(right[i]);
}
return sb.ToString();
}
And so you can put it
String a = "abc";
String b = "defg";
// adcf
String output1 = Merge(a, b, 2, 0);
// beg
String output2 = Merge(a, b, 2, 1);

it happens because B has longer words than A. So when its iteration is bigger than A' length, it will cause an error.
so you need to check whether A has that much word, before adding it
IF B' length always greater than A, then you can use bellow code
class Program
{
static void Main(string[] args)
{
string a= "First";
string b= "MiddleName";
string newstring = "";
string newstring1 = "";
int length = b.Length;
for (int l = 0; l < length; l=l+1)
{
if(l%2==0)
{
if(a.Length > l)
{newstring += a[l].ToString();}
newstring += b[l].ToString();
}
if (l % 2 == 1)
{
if(a.Length > l)
{newstring1 += a[l].ToString();}
newstring1 += b[l].ToString();
}
}
Console.ReadLine();
}
}

for (int l = 0; l < b.length && l < a.length; l++)
{
if(l%2==0)
{
newstring += a[l]+ b[l];
}
if (l % 2 == 1)
{
newstring1 += a[l] + b[l];
}
}

C# Hangman IndexOf Loop

I am a beginner in C# and i am trying to make a "hangman" game. I got stuck at the process when the player guess a letter.
If the word for example is DATA, the application only gets the first A in DATA.
I understand that i have to loop the word to get all the A´s but i am having touble with making it work!
here is my code for the method myGuess:
public void myGuess(String letter)
{
int plats = 0;
string wordToGuess = label4.Text;
plats = wordToGuess.IndexOf(letter);
string wordToShow = label5.Text;
//ersätt "_" med bokstaven på alla positioner bokstaven dyker upp
wordToShow = wordToShow.Substring(0, wordToGuess.IndexOf(letter)) + letter +
wordToShow.Substring(plats + 1, wordToShow.Length - (plats + 1));
label5.Text = wordToShow;
}
I have been trying to google it but because i am a beginner i don't understand the
suggestions people give. Hopefully it is a way to loop for more than one letter with IndexOf?

IndexOf returns the index of the first instance of the character in the string. You could manipulate your string using substring, but you'd be making it more complicated than you need to need. Instead, you can just loop through each of the characters in the String with a for loop:
for (int i = 0; i < wordToGuess.Length; i++ )
{
if (WordToGuess[i] == letter)
{
//Update the correctly guessed letters, (using value of i to determine which letter to make visible.)
}
}
label5.Text = wordToShow;

You can use this:
label4(wordToGuess): DATA
label5(wordToShow): ****
When you call myGuess('A')
label4(wordToGuess): DATA
label5(wordToShow): *A*A
When you call myGuess('T')
label4(wordToGuess): DATA
label5(wordToShow): *ATA
...
public void myGuess(char letter)
{
string wordToGuess = label4.Text;
string wordToShow = label5.Text;
if (wordToShow.Length == 0)
{
for (int i = 0; i < wordToGuess.Length; i++)
wordToShow += "*";
}
for (int i = 0; i < wordToGuess.Length; i++)
{
if (wordToGuess[i] == letter || wordToGuess[i] == wordToShow[i])
wordToShow = wordToShow.Remove(i,1).Insert(i, Char.ToString(letter));
}
label5.Text = wordToShow;
}

Here's a long solution that's probably overly generic.
List<int> findIndexes(string myStr, char letter)
{
var foundIndexes = new List<int>();
for (int i = 0; i < myStr.Length; i++)
{
if (myStr[i] == letter)
foundIndexes.Add(i);
}
return foundIndexes;
}
string ReplaceIndex(string s, int index, char letter){
return s.Substring(0, index )
+ letter
+ s.Substring(index + 1, s.Length - (index + 1));
}
void Main()
{
string s= "data";
string wordToShow = "____";
var letter = 'a';
var indexes = findIndexes(s, letter);
foreach (var index in indexes)
{
wordToShow = ReplaceIndex(wordToShow, index, letter);
}
Console.WriteLine (wordToShow);
}

A simple for loop should handle it.
for (int i = 0; i < wordToGuess.Length; i++)
{
if (wordToGuess[i].ToString().Equals(letter.ToString(), System.StringComparison.InvariantCultureIgnoreCase))
{
wordToShow = string.Format("{0}{1}{2}", wordToShow.Substring(0, i), letter, wordToShow.Substring(i, wordToShow.Length - (i + 1)));
}
}
Here's a fiddle: http://dotnetfiddle.net/UATeVJ

Counting how many times a certain char appears in a string before any other char appears

I have many strings. Each string is prepended with at least 1 $. What is the best way to loop through the chars of each string to count how many $'s there are per string.
eg:
"$hello" - 1
"$$hello" - 2
"$$h$ello" - 2

You could use the Count method
var count = mystring.Count(x => x == '$')

int count = myString.TakeWhile(c => c == '$').Count();
And without LINQ
int count = 0;
while(count < myString.Length && myString[count] == '$') count++;

The simplest approach would be to use LINQ:
var count = text.TakeWhile(c => c == '$').Count();
There are certainly more efficient approaches, but that's probably the simplest.

You could do this, it doesn't require LINQ, but it's not the best way to do it(since you make split the whole string and put it in an array and just pick the length of it, you could better just do a while loop and check every character), but it works.
int count = test.Split('$').Length - 1;

var str ="hello";
str.Where(c => c == 'l').Count() // 2

int count = yourText.Length - yourText.TrimStart('$').Length;

int count = Regex.Matches(myString,"$").Count;

public static int GetHowManyTimeOccurenceCharInString(string text, char c)
{
int count = 0;
foreach(char ch in text)
{
if(ch.Equals(c))
{
count++;
}
}
return count;
}

just a simple answer:
public static int CountChars(string myString, char myChar)
{
int count = 0;
for (int i = 0; i < myString.Length; i++)
{
if (myString[i] == myChar) ++count;
}
return count;
}
Cheers! - Rick

One approach you could take is the following method:
// Counts how many of a certain character occurs in the given string
public static int CharCountInString(char chr, string str)
{
return str.Split(chr).Length-1;
}
As per the parameters this method returns the count of a specific character within a specific string.
This method works by splitting the string into an array by the specified character and then returning the length of that array -1.

//This code worked for me
class CountOfLettersOfString
{
static void Main()
{
Console.WriteLine("Enter string to check count of letters");
string name = Console.ReadLine();
//Method1
char[] testedalphabets = new char[26];
int[] letterCount = new int[26];
int countTestesd = 0;
Console.WriteLine($"Given String is:{name}");
for (int i = 0; i < name.Length - 1; i++)
{
int countChar = 1;
bool isCharTested = false;
for (int j = 0; j < testedalphabets.Length - 1; j++)
{
if (name[i] == testedalphabets[j])
{
isCharTested = true;
break;
}
}
if (!isCharTested)
{
testedalphabets[countTestesd] = name[i];
for (int k = i + 1; k < name.Length - 1; k++)
{
if (name[i] == name[k])
{
countChar++;
}
}
letterCount[countTestesd] = countChar;
countTestesd++;
}
else
{
continue;
}
}
for (int i = 0; i < testedalphabets.Length - 1; i++)
{
if (!char.IsLetter(testedalphabets[i]))
{
continue;
}
Console.WriteLine($"{testedalphabets[i]}-{letterCount[i]}");
}
//Method2
var g = from c in name.ToLower().ToCharArray() // make sure that L and l are the same eg
group c by c into m
select new { Key = m.Key, Count = m.Count() };
foreach (var item in g)
{
Console.WriteLine(string.Format("Character:{0} Appears {1} times", item.Key.ToString(), item.Count));
}
Console.ReadLine();
}
}

This is a similar Solution to find how many email addresses included in a string. This way is more efficient`
int count = 0;
foreach (char c in email.Trim())
if (c == '#') count++;