Problem Description

Given a string, find the length of the longest substring T that contains at most 2 distinct characters.

For example, Given s = “eceba”,

T is "ece" which its length is 3. 

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has a nice solution to this problem using the sliding window technique. The code is rewritten as follows.

1 class Solution { 2 public: 3     int lengthOfLongestSubstringTwoDistinct(string s) { 4         int l = 0, r = -1, len = 0, n = s.length(); 5         for (int k = 1; k < n; k++) { 6             if (s[k] == s[k - 1]) continue; 7             if (r >= 0 && s[k] != s[r]) { 8                 len = max(len, k - l); 9                 l = r + 1;10             }11             r = k - 1;12         }13         return max(n - l, len);14     }15 };