python

 class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        i,ans = 0,0
        t = [0] * 128
        for j, char in enumerate(s):
            t[ord(char)] += 1
            while(t[ord(char)] > 1):
                t[ord(s[i])] -= 1
                i += 1
            ans = max(ans, j - i + 1)
        return ans

java

 class Solution {
    public int lengthOfLongestSubstring(String s) {
        int[] t = new int[128];
        int ans = 0;
        for(int i = 0, j = 0; j < s.length(); j++){
            t[s.charAt(j)] ++;
            while(t[s.charAt(j)] > 1){
                t[s.charAt(i++)] --;
            }
            ans = Math.max(ans, j - i  + 1);
        }
        return ans;
    }
}

HashSet-JAVA/PYTHON

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int res = 0;
        Set<Character> t = new HashSet<>();
        for(int i = 0,j = 0; j < s.length(); j++){
            //如果【i,j】中有重复字符出现, 移除set中的元素且右移,直到使得【i,j】无重复为止
            while (t.contains(s.charAt(j)))
                t.remove(s.charAt(i++));
            t.add(s.charAt(j));
            res = Math.max(res, j - i+1);
        }
        return res;
    }
}

// PYTHON

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        t = set()
        i, res = 0, 0
        for j, char in enumerate(s):
            # 持续移除哈希表中s[i, ==char]
            while(char in t):
                t.remove(s[i])
                i += 1
            t.add(char)
            res = max(res, j - i + 1)
        return res