CODEWITHSUNDEEP
c#string
user4563563
user4563563

Reputation:

Return index of longest substring

How do I return the index of d in the following string "abbcccddddcccbba" I know how to find the longest substring but retruning the starting index is eluding me.

public static int IndexOfLongestRun(string str)
    {
        int currentIndex = 0;

        int finalIndex = 0;

        int longestOccurence = 0;

        for (int i = 0; i < str.Length - 1; i++)
        {
            if (str[i] == str[i + 1])
            {
                currentIndex++;
            }

            else
            {
                currentIndex = 1; 
            }

            if (longestOccurence < currentIndex)
            {
                longestOccurence = currentIndex;
            }
        }


        return str.IndexOf(str, longestOccurence); // return what???
    }

Upvotes: 2

Views: 205

Answers (1)

Joel Bourbonnais
Joel Bourbonnais

Reputation: 2718

I tested the following and I think it is the most efficient way:

public static int IndexOfLongestRun(string str)
{
  if (string.IsNullOrEmpty(str)) return -1;

  int currentStartIndex = 0;
  int longestIndex = 0;
  int longestLength = 0;
  int currentLenght = 0;

  for (int i = 0; i < str.Length - 1; i++)
  {
    if (str[i] != str[i + 1])
    {
      currentStartIndex = i + 1;
      currentLenght = 1;
    }
    else
    {
      currentLenght++;
    }

    if (currentLenght > longestLength)
    {
      longestLength = currentLenght;
      longestIndex = currentStartIndex;
    }
  }

  return longestIndex;
}

Upvotes: 4

Related Questions