Given a string, find the length of the longest substring without repeating characters.
Examples:
Given "abcabcbb", the answer is "abc", which the length is 3.
Given "bbbbb", the answer is "b", with the length of 1.
Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.
記錄每個字母上一次出現(xiàn)的位置，將位置存儲在map中，每次遇到下一個字母便在map中查找這個字母上次遇到的位置筋遭，獲取這段距離，用num記錄最大值并返回桨武。
int lengthOfLongestSubstring(string s) {
if (s.length() == 0) return 0;
map<char, int> mp;
int num = 0;
for (int i = 0, j = 0; i < s.length(); i++) {
map<char, int>::iterator it = mp.find(s[i]);
if (it != mp.end()) {
j = max(j, mp[s[i]] + 1);
}
mp[s[i]] = i;
num = max(num, i - j + 1);
}
return num;
}
