Description

Submission

class Solution {
public:
    string licenseKeyFormatting(string s, int k) {
        string ret;
        int cnt = 0;
        for(int i = s.length() - 1; i >= 0; --i) {
            if(s[i] == '-') continue;
            if(cnt != 0 && cnt % k == 0) ret.push_back('-');
            ret.push_back(toupper(s[i]));
            ++cnt;
        }
        reverse(ret.begin(), ret.end());
        return ret;
    }
};