Leetcode 159. Longest Substring with At Most Two Distinct Characters (Hard) (cpp)

Leetcode 159. Longest Substring with At Most Two Distinct Characters (Hard) (cpp)

Tag: Hash Table, Two Pointers, String

Difficulty: Hard

/*

159. Longest Substring with At Most Two Distinct Characters (Hard)

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.

*/
class Solution {
public:
	int lengthOfLongestSubstringTwoDistinct(string s) {
		if (s.size() < 3) {
			return s.size();
		}
		vector t(256, 0);
		int sl = 0, f = 0, res = 0, cnt = 0;
		while (f < s.size()) {
			if (++t[s[f++]] == 1) {
				cnt++;
			}
			while (cnt > 2) {
				--t[s[sl++]];
				if (t[s[sl - 1]] == 0) {
					cnt--;
				}
			}
			res = max(f - sl, res);
		}
		return res;
	}
};