【leetcode】Longest Substring Without Repeating Characters

https://leetcode.com/problems/longest-substring-without-repeating-characters/

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.

思路：

用hash方法，申请locs，记录某个字符（比如a）上一次出现的位置，idx记录当前没有重复子串的起始位置的前一个位置（初值-1）。如果比idx大的下标更新后，这个字符再次出现，那么locs[s[i]] > idx，这时，idx指向指向与当前字符相同的位置，也就是当前不重复子串的前一个位置。

class Solution {public:    int lengthOfLongestSubstring(string s) {        vector<int> locs(256, -1);        int idx = -1, max = 0;for (int i=0, sz=s.size(); i<sz; ++i) {            if (locs[s[i]] > idx) idx = locs[s[i]];            if (i - idx > max) max = i - idx;            locs[s[i]] = i;        }        return max;    }};