binary-watch

Binary Watch – LeetCode 401

Problem

Description

A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).

Each LED represents a zero or one, with the least significant bit on the right.

Example

Input: n = 1
Return: [“1:00”, “2:00”, “4:00”, “8:00”, “0:01”, “0:02”, “0:04”, “0:08”, “0:16”, “0:32”]

Answer

Original

Code

class Solution {
public:
    vector<string> readBinaryWatch(int num) {
        vector<string> rs;
        for (int h = 0; h < 12; h++)
            for (int m = 0; m < 60; m++)
                if (bitset<10>(h << 6 | m).count() == num)
                    rs.emplace_back(to_string(h) + (m < 10 ? ":0" : ":") + to_string(m));
        return rs;
    }
};

思路

总共72种方案，索性先生成再验证，时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$2$ ms，排名$53.95\%$

Better

还没看到更好的思路。