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  1. Prepare
  2. Algorithms
  3. Strings
  4. Palindrome Index
  5. Discussions

Palindrome Index

  • jmstr8261
     + 0 comments

    C# failed first tests using if(s == s,Reverse()) It was too slow for the tests - I'd still use it in production for readability though. Here's the final:

    public static int palindromeIndex(string s)
{
    int stringLength = s.Length;            
    int returnPos = 0;

    if (IsReversible(s))
        return -1;

    for (int i = 0; i < stringLength/2; i++)
    {
        if (s[i] != s[stringLength-i-1])
        {
            returnPos = RemoveCharacterAndTest(s, i);
            if (returnPos>-1)
                return returnPos;
        }
    }
    return -1;
}

private static int RemoveCharacterAndTest(string s, int removeAt)
{
    string testString = s.Remove(removeAt,1);
    int returnPos = 0;
    if (IsReversible(testString))
        return removeAt;

    testString = s.Remove(s.Length - removeAt - 1, 1);
    if (IsReversible(testString))
    {
        returnPos = (s.Length - removeAt - 1);
        return returnPos;
    }                
    return -1;
}

private static bool IsReversible(string s)
{
    int strLength = s.Length;
    for (int i = 0; i < strLength / 2; i++)
    {
        if (s[i] != s[strLength - i - 1])
            return false;
    }
    return true;
}