classSolution{
public:intlengthOfLongestSubstring(string s){
int left =0, right =0, ans =0;int len = s.length();
unordered_set<char> vis;while(left < len){
//右指针移动,窗口增大while(right < len &&!vis.count(s[right])){
vis.insert(s[right]);
right++;}//维护一个最长子串
ans =max(ans,right - left);//左指针移动
vis.erase(s[left]);
left ++;}return ans;}};