[LeetCode] Longest Substring with At Most Two Distinct Characters

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

class Solution {
public:
    int lengthOfLongestSubstringTwoDistinct(string s) {
        int l = 0, r = -1, len = 0, n = s.length();
        for (int k = 1; k < n; k++) {
            if (s[k] == s[k - 1]) continue;
            if (r >= 0 && s[k] != s[r]) {
                len = max(len, k - l);
                l = r + 1;
            }
            r = k - 1;
        }
        return max(n - l, len);
    }
};