leetcode681

class Solution {
public:
    string nextClosestTime(string time) {
        vector<int> vi;
        for (char c : time) {
            if (c == ':') continue;
            vi.push_back(c - '0');
        }
        int hh = vi[0] * 10 + vi[1];
        int mm = vi[2] * 10 + vi[3];
        int original = hh * 60 + mm;
        sort(vi.begin(), vi.end());
        int ans = INT_MAX;
        set<int> candidates;
        for (int i = 0; i < 4; ++i) {
            for (int j = 0; j < 4; ++j) {
                for (int k = 0; k < 4; ++k) {
                    for (int l = 0; l < 4; ++l) {
                        int hh = vi[i] * 10 + vi[j];
                        int mm = vi[k] * 10 + vi[l];
                        if (hh >= 24 || mm >= 60) continue;
                        int candidate = hh * 60 + mm;
                        if (candidate <= 1440) {
                            candidates.insert(candidate);
                        }
                    }
                }
            }
        }
        for (auto candidate : candidates) {
            if (candidate > original) {
                ans = min(ans, candidate);
            }
        }
        if (ans == INT_MAX) {
            ans = *(candidates.begin());
        }
        hh = ans / 60;
        mm = ans % 60;
        string str_hh = hh < 10 ? "0" + to_string(hh) : to_string(hh);
        string str_mm = mm < 10 ? "0" + to_string(mm) : to_string(mm);
        return str_hh + ":" + str_mm;
    }
};