【LeetCode】401. Binary Watch

题目描述:

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.

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”.

代码实现:

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