Sherlock considers a string to be valid if all characters of the string appear the same number of times. It is also valid if he can remove just character at index in the string, and the remaining characters will occur the same number of times. Given a string , determine if it is valid. If so, return YES, otherwise return NO.

sherlock_and_the_valid_string.cpp

string isValid(string s) {
    std::map<char, int> freq;
    vector<int> list;
    vector<int> vals;
    vector<int>::iterator list_unique;

    if(s.length() == 1) return "YES";
    else
    {
        for(int i = 0; i < s.length(); i++){
            if(freq.find(s[i]) == freq.end()) freq[s[i]] = 1;
            else freq[s[i]] += 1;
        }

        for(auto const& i: freq) list.insert(list.end(), i.second);
        vals = list;

        sort(list.begin(), list.end());
        list_unique = std::unique(list.begin(), list.end());
        list.resize(std::distance(list.begin(),list_unique)); 

        if(list.size() == 1){
            return "YES";
        }
        else if(std::count(vals.begin(), vals.end(), 1) > 1){
            return "NO";
        }
        else if(list.size() == 2 and (std::find(list.begin(), list.end(), 1) != list.end() or abs(list[0] - list[1]) == 1)){
                return "YES";
        }
        else return "NO";
    }
}