LeetCode | 401. Binary Watch

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#leetcode #算法 #Binary Watch

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此篇博客讨论了如何编写一个算法，给定特定数量的LED亮起，找出二进制手表可能表示的所有时间。重点在于理解时间的二进制表示法和如何通过编程实现解决方案。

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题目

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.

For example, the below binary watch reads “4:51”.
在这里插入图片描述

Given an integer turnedOn which represents the number of LEDs that are currently on, return all possible times the watch could represent. You may return the answer in any order.

The hour must not contain a leading zero.

For example, “01:00” is not valid. It should be “1:00”.
The minute must be consist of two digits and may contain a leading zero.

For example, “10:2” is not valid. It should be “10:02”.

Example 1:

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

Example 2:

Input: turnedOn = 9
Output: []

Constraints:

0 <= turnedOn <= 10

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代码

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