LeetCode 401. Binary Watch

101 阅读 0 评论 67 点赞

我是靠谱客的博主淡淡枕头，最近开发中收集的这篇文章主要介绍LeetCode 401. Binary Watch，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

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.

For example, the above binary watch reads "3:25".

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"]

Note:

The order of output does not matter.
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".

DFS，先枚举灯的个数，然后根据个数搜索。

class Solution {
public:
    int re[6] = {1, 2, 4, 8, 16, 32};
    int hours[4] = {0, 0, 0, 0};
    int minutes[6] = {0, 0, 0, 0, 0, 0};
    vector<string> v;
    void dfsh(int start, int numh, int numm){
        if(start == 4 && numh) return; 
        if(!numh){
            dfsm(0, numm);
        }else{
            hours[start] = 1;
            dfsh(start + 1, numh - 1, numm);
            hours[start] = 0;
            dfsh(start + 1, numh, numm);
        }
    }
    void dfsm(int start, int numm){
        if(start == 6 && numm) return; 
        if(!numm){
            int h = 0, m = 0, i;
            for(i = 0; i < 4; i ++){
                if(hours[i]) h += re[i];
            }
            for(i = 0; i < 6; i ++){
                if(minutes[i]) m += re[i];
            }
            string tmp = "";
            if(h > 11 || m > 59) return;
            tmp = to_string(h) + ":";
            if(m < 10) tmp += "0" + to_string(m);
            else tmp += to_string(m);
            v.push_back(tmp);
        }else{
            minutes[start] = 1;
            dfsm(start + 1, numm - 1);
            minutes[start] = 0;
            dfsm(start + 1, numm);
        }
    }
    vector<string> readBinaryWatch(int num) {
        int i;
        for(i = 0; i <= 4; i ++){
            if(num - i <= 6 && num - i >= 0){
                dfsh(0, i, num - i);
            }
        }
        return v;
    }
};