/*
Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.
Example 2:

Input: “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.
Example 3:

Input: “pwwkew”
Output: 3
Explanation: 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.
*/

/*
整体思路：
	使用vector<int> dic(255, -1)进行数据的保存， 
*/

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        vector<int> dic(255,-1);	//巧妙的利用了数组的特性  数组的下标表示对应的字符，
					//存储的元素保存该字符在元字符串中的位置 
        int maxLen = 0;		//保存最大不重复子串的长度 
        int start = -1;		//保存前面不重复的位置 
        for(int i = 0; i < s.size(); i++){
            if(dic[s.at(i)] > start){
                start = dic[s.at(i)];
            }
            dic[s.at(i)] = i;
            maxLen = max(maxLen, i - start);
        }
        return maxLen;
    }
};

//lambda表达式 
//https://www.cnblogs.com/langzou/p/5962033.html
static int x = []() {
    std::ios::sync_with_stdio(false);	//sync_with_stdio()函数有打开或关闭使用C++风格I/O系统混合C风格的I/O系统的功能。 
    std::cin.tie(NULL);			//取消cin和cout的绑定
    std::cout.tie(0);				
    return 0;
}();

开始的时候巨懵逼，查看运行速度比较快的代码都会有这一块的东西，就随手查了一下，这一堆东西属于lambda，有兴趣的可以参考这一篇博客
https://www.cnblogs.com/langzou/p/5962033.html