leetcode 401: Binary Watch

解题思路:
本题灯的个数,其实就是二进制位中1的个数。最简单的做法,遍历所有时间,如果hour和minute的二进制值中的1的个数满足要求,当前时间就是一个解元素。不过这种方法耗时较长。

原题目:

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.

leetcode 401: Binary Watch_第1张图片

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".

AC解,C++代码,菜鸟一个,请大家多多指正

class Solution {
public:
    vector<string> readBinaryWatch(int num) {
        vector<string> ret;
        stringstream stream;
        for (int hour = 0; hour < 12; hour++) {
            for (int minute = 0; minute < 60; minute++) {
                bitset<10> value = (hour << 6) + minute;
                if (value.count() == num) {
                    string ret_time;
                    stream.clear();
                    stream << hour << ":";
                    if (minute < 10) {
                        stream << "0";
                    }
                    stream << minute;
                    stream >> ret_time;
                    ret.push_back(ret_time);
                }
            }
        }
        return ret;
    }
};

你可能感兴趣的:(leetcode)