[387] First Unique Character in a String

【题目描述】

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.

【解题思路】

用哈希表扫描两遍即可

【代码】

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