Longest Substring Without Repeating Characters

Given a string, find the length of thelongest substringwithout repeating characters.

Examples:

Given"abcabcbb", the answer is"abc", which the length is 3.

Given"bbbbb", the answer is"b", with the length of 1.

Given"pwwkew", the answer is"wke", with the length of 3. Note that the answer must be asubstring,"pwke"is asubsequenceand not a substring.

Tips:

注意循环条件，用两个指针来做。

Code：

public class Solution {
    public int lengthOfLongestSubstringTwoDistinct(String s) {
        int res = 0, left = 0;
        Map<Character, Integer> map = new HashMap<>();
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (!map.containsKey(s.charAt(i))) map.put(c, 0);
            map.put(c, map.get(c) + 1);
            while (map.size() > 2) {
                char l = s.charAt(left);
                map.put(l, map.get(l) - 1);
                if (map.get(l) == 0) map.remove(l);
                left++;
            }
            res = Math.max(res, i - left + 1);
        }
        return res;
    }
}