Leetcode 159 Solution

This article provides solution to leetcode question 159 (longest-substring-with-at-most-two-distinct-characters)
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https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters

Solution

class Solution {
public:
    int lengthOfLongestSubstringTwoDistinct(string s) {
        map<char, int> m;
        int l = 0;
        int max_len = 0;
        for (int i = 0; i < s.size(); i++)
        {
            m[s[i]]++;

            while (l <= i && m.size() > 2)
            {
                auto ch = s[l++];
                m[ch]--;
                if (m[ch] == 0)
                    m.erase(ch);
            }

            max_len = max(max_len, i - l + 1);
        }

        return max_len;
    }
};