[LeetCode3]Longest Substring Without Repeating Characters

题目：

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.

分类：Hash Table  Two Pointers String

代码：

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        map<char,int> hash;
        int start = -1;
        int maxLength = 0;
        for(int i = 0; i < s.size(); ++i)
        {
            if(hash.count(s[i]) != 0)
            {
                start = max(start,hash[s[i]]);
            }
            hash[s[i]] = i;
            maxLength = max(maxLength,i-start);
        }
        return maxLength;
    }
};