class Solution {
public:
int lengthOfLongestSubstring(string s) {
int p[256];
memset(p,-1,sizeof(p));
int ans = 0, flag = -1;
for(int i = 0;i < s.length();i++){
flag = max(flag,p[s[i]]);
p[s[i]] = i;
ans = max(ans,i-flag);
}
return ans;
}
};