0387-first-unique-character-in-a-string.cpp

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