LeetCode 3. Longest Substring Without Repeating Characters C++

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.

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        vector<int> dict(256,-1);
        int start=-1,maxlen=0;
        for(int i=0;i<s.length();i++){
            if(dict[s[i]]>start)
                start=dict[s[i]];
            dict[s[i]]=i;
            maxlen=max(maxlen,i-start);
        }
        return maxlen;
    }
};

字符强制转换为int之后，都可以得到其对应的ASCII值（应该是这样，有错欢迎指正），所以有vector<int> dict(256,-1);

以aabbcdeff为例

i	char	start	max(maxlen,i-start)
0	a	-1	(0,1)
1	a	0	(1,1)
2	b	0	(1,2)
3	b	2	(2,1)
4	c	2	(2,2)
5	d	2	(2,3)
6	e	2	(3,4)
7	f	2	(4,5)
8	f	7	(5,1)