LeetCode [159] Longest Substring with At Most Two Distinct Characters

159. Longest Substring with At Most Two Distinct Characters

Medium

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

Example 1:

Input: "eceba"
Output: 3
Explanation: t is "ece" which its length is 3.

Example 2:

Input: "ccaabbb"
Output: 5
Explanation: t is "aabbb" which its length is 5.

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class Solution { public: int lengthOfLongestSubstringTwoDistinct(string s) { int n = s.size(), i = 0, j = 0, maxLen = 0; map<char, int> mp; while(j<n){ mp[s[j]]++; while(mp.size()>2){ if(--mp[s[i]]==0){ mp.erase(s[i]); } i++; } if(j-i+1>maxLen) maxLen = j-i+1; j++; } return maxLen; } }; class Solution { public: int lengthOfLongestSubstringTwoDistinct(string s) { int n = s.size(), ndiff = 0, l = 0, r = 0, len = 0; vector<int> hash(128, 0); while(r<n){ int c = s[r++]; hash[c]++; if(hash[c]==1){ ndiff++; while(ndiff>2){ int c1 = s[l++]; hash[c1]--; if(hash[c1]==0) ndiff--; } } len = max(len, r-l); } return len; } };