Leetcode-387 First Unique Character in a String

#387.   First Unique Character in a String      

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.

题解：词频统计。

class Solution {
public:
    int firstUniqChar(string s) {
        vector<int> nums(26);
        for(int i=0;i<s.size();i++)
        {
            nums[s[i]-'a']++;
        }
        for(int i=0;i<s.size();i++)
        {
            if(nums[s[i]-'a']==1)
            {
                return i;
            }
                
        }
        return -1;
    }
};