Problem

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.
Note: You may assume the string contain only lowercase letters.

Example

s = "leetcode"
return 0.

s = "loveleetcode",
return 2.

Code

static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    int firstUniqChar(string s) {
        long table[256] = {0};
        for(int i=0;i<s.size();i++){
            table[s[i]]++;
        }
        for(int i=0;i<s.size();i++){
            if(table[s[i]]==1)
                return i;
        }
        return -1;
    }
};

Result

387. First Unique Character in a String.png