387. First Unique Character in a String

1. 问题描述

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.

2. 解题思路
3. 代码

class Solution {
public:
    int firstUniqChar(string s)
    {
        std::map<char, int> m1;
        for (int i=0; i<s.size(); i++)
        {
            m1[s[i]]++;
        }

        for (int i=0; i<s.size(); i++)
        {
            if (1 == m1[s[i]])
            {
                return i;
            }
        }
        return -1;
    }
};

4. 反思