longest substring
Examples:
"abcabcbb", the answer is "abc", which the length is 3."bbbbb", the answer is "b", with the length of 1."pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence
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class Solution {
public:
int lengthOfLongestSubstring(string s) {
if (s.empty()) return 0;
if (s.size() == 1) return 1;
vector<int> hash(256, -1);
int i = 0, j = 1;
int res = 0;
hash[s[0]] = 0;
while (j<s.size()){
if (hash[s[j]] >= i){
i = hash[s[j]] + 1;
}
hash[s[j]] = j;
res = max(res, j - i + 1);
j++;
}
return res;
}
};