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How to return the char, of a loops next position, in a char array?

I want to replace a string (that the user inputs) with the next character in the alphabet. I'm having trouble returning the next value from my loop.
Error message: Index was outside the bounds of the array.
I understand that the array ends, and that might be a problem from the +1 I entered. How would I go about solving this?
string inputString = "abcdefghijklmnopqqrstuvxyz";
char[] inputCharArray = inputString.ToCharArray();
char[] alphabetArray = "abcdefghijklmnopqrstuvxyz".ToArray();
var resultStr = "";
for (int i = 0; i < inputCharArray.Length; i++)
{
if(alphabetArray.Contains(inputCharArray[i]))
resultStr += inputCharArray[i+1];
else
resultStr += inputCharArray[i];
}
System.Console.WriteLine(resultStr);

You're getting an Out Of Range exception because i will eventually equal the last index of your input array, and adding 1 to that number is beyond what the array has.
First, make it easier on yourself by making a function to convert a single char into the next letter.
Note, this answer assumes that you want to "wrap around" - the next letter after "z" goes back to "a".
char NextLetter(char input)
{
if (input < 'a' || input > 'z') // simple validation
throw new ArgumentException();
input += (char)1; // go to the next char value
if (input > 'z') // did you go past z?
input = 'a'; // go back to a
return input;
}
Yes, you can also do modulo, this method is the simple version.
Now you can loop through all the letters in your input to construct the output string. In addition, you don't need to .ToCharArray() a string - a string already implements IEnumerable<char>.
var input = "abcxyz";
var outputBuilder = new StringBuilder();
foreach (char letter in input)
{
outputBuilder.Append(NextLetter(letter));
}
Console.WriteLine(outputBuilder.ToString());
// prints "bcdyza"

You can use Array.IndexOf to find the index of the current character in the alphabet, then you can use the modulo operator (%) to get the index of the next character in the alphabet (assuming the alphabet wraps from z to a in your desired solution):
string inputString = "abcdefghijklmnopqqrstuvxyz";
char[] inputCharArray = inputString.ToCharArray();
char[] alphabetArray = "abcdefghijklmnopqrstuvxyz".ToArray();
var resultStr = "";
for (var i = 0; i < inputCharArray.Length; i++)
{
var indexInAlphabet = Array.IndexOf(alphabetArray, inputCharArray[i]);
var indexOfNextLetter = (indexInAlphabet + 1) % alphabetArray.Length;
resultStr += alphabetArray[indexOfNextLetter];
}
Console.WriteLine(resultStr);

C#: Need to split a string into a string[] and keeping the delimiter (also a string) at the beginning of the string

I think I am too dumb to solve this problem...
I have some formulas which need to be "translated" from one syntax to another.
Let's say I have a formula that goes like that (it's a simple one, others have many "Ceilings" in it):
string formulaString = "If([Param1] = 0, 1, Ceiling([Param2] / 0.55) * [Param3])";
I need to replace "Ceiling()" with "Ceiling(; 1)" (basically, insert "; 1" before the ")").
My attempt is to split the fomulaString at "Ceiling(" so I am able to iterate through the string array and insert my string at the correct index (counting every "(" and ")" to get the right index)
What I have so far:
//splits correct, but loses "CEILING("
string[] parts = formulaString.Split(new[] { "CEILING(" }, StringSplitOptions.None);
//splits almost correct, "CEILING(" is in another group
string[] parts = Regex.Split(formulaString, #"(CEILING\()");
//splits almost every letter
string[] parts = Regex.Split(formulaString, #"(?=[(CEILING\()])");
When everything is done, I concat the string so I have my complete formula again.
What do I have to set as Regex pattern to achieve this sample? (Or any other method that will help me)
part1 = "If([Param1] = 0, 1, ";
part2 = "Ceiling([Param2] / 0.55) * [Param3])";
//part3 = next "CEILING(" in a longer formula and so on...

As I mention in a comment, you almost got it: (?=Ceiling). This is incomplete for your use case unfortunately.
I need to replace "Ceiling()" with "Ceiling(; 1)" (basically, insert "; 1" before the ")").
Depending on your regex engine (for example JS) this works:
string[] parts = Regex.Split(formulaString, #"(?<=Ceiling\([^)]*(?=\)))");
string modifiedFormula = String.join("; 1", parts);
The regex
(?<=Ceiling\([^)]*(?=\)))
(?<= ) Positive lookbehind
Ceiling\( Search for literal "Ceiling("
[^)] Match any char which is not ")" ..
* .. 0 or more times
(?=\)) Positive lookahead for ")", effectively making us stop before the ")"
This regex is a zero-assertion, therefore nothing is lost and it will cut your strings before the last ")" in every "Ceiling()".
This solution would break whenever you have nested "Ceiling()". Then your only solution would be writing your own parser for the same reasons why you can't parse markup with regex.

Regex.Replace(formulaString, #"(?<=Ceiling\()(.*?)(?=\))","$1; 1");
Note: This will not work for nested "Ceilings", but it does for Ceiling(), It will also not work fir Ceiling(AnotherFunc(x)). For that you need something like:
Regex.Replace(formulaString, #"(?<=Ceiling\()((.*\((?>[^()]+|(?1))*\))*|[^\)]*)(\))","$1; 1$3");
but I could not get that to work with .NET, only in JavaScript.

This is my solution:
private string ConvertCeiling(string formula)
{
int ceilingsCount = formula.CountOccurences("Ceiling(");
int startIndex = 0;
int bracketCounter;
for (int i = 0; i < ceilingsCount; i++)
{
startIndex = formula.IndexOf("Ceiling(", startIndex);
bracketCounter = 0;
for (int j = 0; j < formula.Length; j++)
{
if (j < startIndex) continue;
var c = formula[j];
if (c == '(')
{
bracketCounter++;
}
if (c == ')')
{
bracketCounter--;
if (bracketCounter == 0)
{
// found end
formula = formula.Insert(j, "; 1");
startIndex++;
break;
}
}
}
}
return formula;
}
And CountOccurence:
public static int CountOccurences(this string value, string parameter)
{
int counter = 0;
int startIndex = 0;
int indexOfCeiling;
do
{
indexOfCeiling = value.IndexOf(parameter, startIndex);
if (indexOfCeiling < 0)
{
break;
}
else
{
startIndex = indexOfCeiling + 1;
counter++;
}
} while (true);
return counter;
}

How to capitalize the first character of every sentence

Create an application with a method that accepts a string as an argument and returns a copy of the string with the first character of each sentence capitalized.
This is what I have to far and I can't seem to get it right:
//Create method to process string.
private string Sentences(string input)
{
//Capitalize first letter of input.
char firstLetter = char.ToUpper(input[0]);
//Combine the capitalize letter with the rest of the input.
input = firstLetter.ToString() + input.Substring(1);
//Create a char array to hold all characters in input.
char[] letters = new char[input.Length];
//Read the characters from input into the array.
for (int i = 0; i < input.Length; i++)
{
letters[i] = input[i];
}
//Loop through array to test for punctuation and capitalize a character 2 index away.
for (int index = 0; index < letters.Length; index++)
{
if(char.IsPunctuation(letters[index]))
{
if (!((index + 2) >= letters.Length))
{
char.ToUpper(letters[index+ 2]);
}
}
}
for(int ind = 0; ind < letters.Length; ind++)
{
input += letters[ind].ToString();
}
return input;
}

You could use Linq.Aggregate n - see comments in code and code output for explanation how it work's.
This one will respect "Bla. blubb" as well - you need to check for whitespaces after ".?!"
using System;
using System.Linq;
internal class Program
{
static string Capitalize(string oldSentence )
{
return
// this will look at oldSentence char for char, we start with a
// new string "" (the accumulator, short acc)
// and inspect each char c of oldSentence
// comment all the Console.Writelines in this function, thats
// just so you see whats done by Aggregate, not needed for it to
// work
oldSentence
.Aggregate("", (acc, c) =>
{
System.Console.WriteLine("Accumulated: " + acc);
System.Console.WriteLine("Cecking: " + c);
// if the accumulator is empty or the last character of
// trimmed acc is a ".?!" we append the
// upper case of c to it
if (acc.Length == 0 || ".?!".Any(p => p == acc.Trim().Last())) // (*)
acc += char.ToUpper(c);
else
acc += c; // else we add it unmodified
System.Console.WriteLine($"After: {acc}\n");
return acc; // this returns the acc for the next iteration/next c
});
}
static void Main(string[] args)
{
Console.SetBufferSize(120, 1000);
var oldSentence = "This is a testSentence. some occurences "
+ "need capitalization! for examlpe here. or here? maybe "
+ "yes, maybe not.";
var newSentence = Capitalize(oldSentence);
Console.WriteLine(new string('*', 80));
Console.WriteLine(newSentence);
Console.ReadLine();
}
}
(*)
".?!".Any(p => p == ... )) means does the string ".?!" contain any character that equals ...
acc.Trim().Last() means: remove whitespaces in front/on end of acc and give me the last character
.Last() and .Any() are also Linq. Most of the Linq-esc extension can be found here: https://msdn.microsoft.com/en-us/library/9eekhta0(v=vs.110).aspx
Output (snipped - its rather longish ;o)
Accumulated:
Cecking: T
After: T
Accumulated: T
Cecking: h
After: Th
Accumulated: Th
Cecking: i
After: Thi
Accumulated: Thi
Cecking: s
After: This
Accumulated: This
Cecking:
After: This
Accumulated: This
Cecking: i
After: This i
Accumulated: This i
Cecking: s
After: This is
<snipp - .. you get the idea how Aggregate works ...>
Accumulated: This is a testSentence.
Cecking: s
After: This is a testSentence. S
<snipp>
Accumulated: This is a testSentence. Some occurences need capitalization!
Cecking: f
After: This is a testSentence. Some occurences need capitalization! F
<snipp>
********************************************************************************
This is a testSentence. Some occurences need capitalization! For examlpe here. Or here? Maybe yes, maybe not.

I would suggest to use a regex to identify all the dots in your sentence. Get the match, make it upper case and replace it back in the original sentence, in the match index. I dont actually have any IDE in which try the code on .NET right now but i can write it in pseudocode for better understanding.
String setence = "your.setence.goes.here";
Regex rx = new Regex("/\..*?[A-Z]/");
foreach (Match match in rx.Matches(sentence))
{
setence.remove(match.Index, 2).insert(match.Index, String.ToUpper(match.Value));
}

You have two tasks:
1) Split text into sentences
2) Capitalize the first char in the sentences
Task one can be very complex, e.g. because there a lot of crazy languages out there. Put since this is homework I assume you can go ahead and simply split by well know separators.
Task two is just about basic string operations. You select the first char, make it uppercase and add the missing part of the sentence via a substring operation.
Here is a code example:
char[] separators = new char[] { '!', '.', '?' };
string[] sentencesArray = "First sentence. second sentence!lastone.".Split(separators, StringSplitOptions.RemoveEmptyEntries);
var i = 0;
Array.ForEach(sentencesArray, e =>
{
sentencesArray[i] = e.Trim().First().ToString().ToUpper() +
e.Trim().Substring(1);
i++;
});

I Have created a method in Groovy for the same
String capitalizeFirstCharInSentence(String str) {
String result = ''
str = str.toLowerCase()
List<String> strings = str.tokenize('.')
strings.each { line ->
StringBuilder builder = new StringBuilder(line)
int i = 0
while (i < builder.size() - 1 && !Character.isLowerCase(builder.charAt(i))) {
i++
}
if (Character.isLowerCase(builder.charAt(i))) {
builder.setCharAt(i, builder.charAt(i).toUpperCase())
result += builder.toString() + '.'
}
}
return result
}

I liked the way you formatted your method because it made it easy for newer coders to read so I decided to try to make the code work while maintaining the structure. The main problem I saw was that you were not replacing the arrays after formatting them.
//Create method to process string.
private string Sentences(string input)
{
//Create a char array to hold all characters in input.
char[] letters = new char[input.Length];
//Read the characters from input into the array.
for (int i = 0; i < input.Length; i++)
{
letters[i] = input[i];
}
//Capitalize first letter of input.
letters[0] = char.ToUpper(letters[0]);
//Loop through array to test for punctuation and capitalize a character 2 index away.
for (int index = 0; index < letters.Length; index++)
{
if(char.IsPunctuation(letters[index]))
{
if (index + 2 <= letters.Length)
{
letters[index + 2] = char.ToUpper(letters[index+ 2]);
}
}
}
// convert array back to string
string results = new string(letters)
return results;
}

C# replace different characters in a string

Everyone knows how to replace a character in a string with:
string text = "Hello World!";
text = text.Replace("H","J");
but what I need is to replace multiple characters in a string
something like:
string text = textBox1.Text;
text = text.Replace("a","b")
text = text.Replace("b","a")
now the result is aa , but if the user types ab I want the result to be ba

There's multiple ways to do this.
Using a loop
char[] temp = input.ToCharArray();
for (int index = 0; index < temp.Length; index++)
switch (temp[index])
{
case 'a':
temp[index] = 'b';
break;
case 'b':
temp[index] = 'a';
break;
}
string output = new string(temp);
This will simply copy the string to a character array, fix each character by itself, then convert the array back into a string. No risk of getting any of the characters confused with any of the others.
Using a regular expression
You can exploit this overload of Regex.Replace:
public static string Replace(
string input,
string pattern,
MatchEvaluator evaluator
)
This takes a delegate that will be called for each match, and return the final result. The delegate is responsible for returning what each match should be replaced with.
string output = Regex.Replace(input, ".", ma =>
{
if (ma.Value == "a")
return "b";
if (ma.Value == "b")
return "a";
return ma.Value;
});

For your particular requirement I would suggest you to use like the following:
string input = "abcba";
string outPut=String.Join("",input.ToCharArray()
.Select(x=> x=='a'? x='b':
(x=='b'?x='a':x))
.ToArray());
The output string will be bacab for this particular input

Do not call String.Replace multiple times for the same string! It creates a new string every time (also it has to cycle through the whole string every time) causing memory pressure and processor time waste if used a lot.
What you could do:
Create a new char array with the same length as the input string. Iterate over all chars of the input strings. For every char, check whether it should be replaced. If it should be replaced, write the replacement into the char array you created earlier, otherwise write the original char into that array. Then create a new string using that char array.
string inputString = "aabbccdd";
char[] chars = new char[inputString.Length];
for (int i = 0; i < inputString.Length; i++)
{
if (inputString[i] == 'a')
{
chars[i] = 'b';
}
else if (inputString[i] == 'b')
{
chars[i] = 'a';
}
else
{
chars[i] = inputString[i];
}
}
string outputString = new string(chars);
Consider using a switch when intending to replace a lot of different characters.

Use should use StringBuilder when you are concatenating many strings in a loop like this, so I suggest the following solution:
StringBuilder sb = new StringBuilder(text.Length);
foreach(char c in text)
{
sb.Append(c == 'a' ? 'b' : 'a');
}
var result = sb.ToString();

Replace consecutive characters with same single character

I was just wondering if there is a simple way of doing this. i.e. Replacing the occurrence of consecutive characters with the same character.
For eg: - if my string is "something likeeeee tttthhiiissss" then my final output should be "something like this".
The string can contain special characters too including space.
Can you guys suggest some simple way for doing this.

This should do it:
var regex = new Regex("(.)\\1+");
var str = "something likeeeee!! tttthhiiissss";
Console.WriteLine(regex.Replace(str, "$1")); // something like! this
The regex will match any character (.) and \\1+ will match whatever was captured in the first group.

string myString = "something likeeeee tttthhiiissss";
char prevChar = '';
StringBuilder sb = new StringBuilder();
foreach (char chr in myString)
{
if (chr != prevChar) {
sb.Append(chr);
prevChar = chr;
}
}

How about:
s = new string(s
.Select((x, i) => new { x, i })
.Where(x => x.i == s.Length - 1 || s[x.i + 1] != x.x)
.Select(x => x.x)
.ToArray());
In english, we are creating a new string based on a char[] array. We construct that char[] array by applying a few LINQ operators:
Select: Capture the index i along with the current character x.
Filter out charaters that are not the same as the subsequent character
Select the character x.x back out of the anonymous type x.
Convert back to a char[] array so we can pass to constructor of string.

Console.WriteLine("Enter any string");
string str1, result="", str = Console.ReadLine();
char [] array= str.ToCharArray();
int i=0;
for (i = 0; i < str.Length;i++ )
{
if ((i != (str.Length - 1)))
{ if (array[i] == array[i + 1])
{
str1 = str.Trim(array[i]);
}
else
{
result += array[i];
}
}
else
{
result += array[i];
}
}
Console.WriteLine(result);
In this code the program ;
will read the string as entered from user
2.Convert the string in char Array using string.ToChar()
The loop will run for each character in string
each character stored in that particular position in array will be compared to the character stored in position one greater than that . And if the characters are found same the character stored in that particular array would be trimmed using .ToTrim()
For last character the loop will show error of index out of bound as it would be the last position value of the array. That's why I used * if ((i != (str.Length - 1)))*
6.The characters left after trimming are stored in result in concatenated form .

word = "something likeeeee tttthhiiissss"
re.sub(r"(.)\1+", r"\1",word)