Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1.

解题思路

设置左右两个指针。左右指针之间的字符没有出现反复，则右指针向右移动。否则左指针向右移动（直到没有反复字符为止）。而且统计最大字符数。

实现代码

// Rumtime: 60 ms
class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        set<int> res;
        int maxLen = 0;
        int left = 0;
        int i;
        for (i = 0; i < s.size(); i++)
        {
            if (res.find(s[i]) != res.end())
            {
                maxLen = max(maxLen, i - left);
                while (s[left] != s[i])
                {
                    res.erase(s[left++]);
                }
                left++;
            }
            else
            {
                res.insert(s[i]);
            }
        }

        maxLen = max(maxLen, i - left);

        return maxLen;
    }
};