# 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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