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  • [LeetCode] Binary Watch

    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".

    给定一个二进制手表,如上图有10个LED组成。给定一个数字代表点亮的LED个数。把亮着的LED所代表的时间返回一个字符串数组。Note中要求了时间输出的格式。

    h << 6 表示h的二进制表示左移6位。

    h << 6 | m表示左移后的二进制与m取或,即h末尾的二进制由m的二进制位代替。

    bitset<10>(h << 6 | m)表示一个10位二进制数,h的二进制前面几位取0构成一个10位二进制数。10个LED。

    count()函数返回bitset<10>(h << 6 | m)中为1的个数。

    class Solution {
    public:
        vector<string> readBinaryWatch(int num) {
            vector<string> res;
            for (int h = 0; h != 12; h++)
                for (int m = 0; m != 60; m++)
                    if (bitset<10>(h << 6 | m).count() == num)
                        res.emplace_back(to_string(h) + (m < 10 ? ":0" : ":") + to_string(m));
            return res;
        }
    };
    // 3 ms
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  • 原文地址:https://www.cnblogs.com/immjc/p/7197640.html
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