LeetCode

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"return 0.s = "loveleetcode",return 2.

Note: You may assume the string contain only lowercase letters.

找出第一个不重复的字母，若没有，返回-1

唔，遍历一遍存每个字母出现过了几次；然后再遍历一遍，当次数为1时返回index

class Solution {public:    int firstUniqChar(string s) {        unordered_map<char, int> vis;        for (int i = 0; i < s.length(); ++i) {            vis[s[i]]++;        }        for (int i = 0; i < s.length(); ++i) {            if (vis[s[i]] == 1) return i;        }        return -1;    }};