Binary Watch问题及解法

问题描述：

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.

Given a non-negative integer n which represents the number of LEDs that are currently on, return all possible times the watch could represent.

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"]

问题分析：

这里用到了一个位集合bitset，大家可以自行了解其用法，这里不多讲述，直接看代码：

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)); // to_string C++ 11支持     return rs;    }};