The task is that I need to remove characters from the string by index from the array. The task with codewars (Last Survivor)?

Question

C++ / C#

All checks passed, but when the check goes with a huge string and a huge array, an error appears

System.IndexOutOfRangeException: Index was outside the bounds of the array

. I must say right away that I know that this error appears when I try to access an index that is not in the array. But I can't figure out why this is happening in my case. PS In this task, arrays with numbers of length 1 less than strings are always given for verification!

public static string LastSurvivor(string letters, int[] coords)
        {
            for (int i = 0; i < coords.Length; i++)
            {
                if (coords[i] > letters.Length) i++;
                letters = letters.Replace(letters[coords[i]].ToString(), "");
            }
            return letters; 
        }

Answer 1

You are doing the problem wrong.
A more correct option would be to create a StringBuilder and write into it all the letters that lie at indices that are not in the coords array.
You can understand why you go beyond the limits yourself - just try step by step to execute this function with the following parameters:
LastSurvivor ("123", new [] {3});