Python:
class Solution(object):def lengthOfLongestSubstring(self, s):""":type s: str:rtype: int"""cnt=defaultdict(int)left =0ans=0for right,c in enumerate(s):cnt[c]+=1while cnt[c]>1:cnt[s[left]]-=1left+=1ans = max(ans,right-left+1)return ans
C++:
class Solution {
public:int lengthOfLongestSubstring(string s) {unordered_map<char,int>cnt;int left=0;int ans=0;int n=s.size();for(int right=0;right<n;right++){cnt[s[right]]++;while(cnt[s[right]]>1){cnt[s[left]]--;left++;}ans = max(ans,right-left+1);}return ans;}
};