LC/401.binary-watch.cpp at main · dtsvivek/LC · GitHub

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/*
 * @lc app=leetcode id=401 lang=cpp
 *
 * [401] Binary Watch
 *
 * https://leetcode.com/problems/binary-watch/description/
 *
 * algorithms
 * Easy (50.79%)
 * Likes:    993
 * Dislikes: 1856
 * Total Accepted:    112K
 * Total Submissions: 220.3K
 * Testcase Example:  '1'
 *
 * A binary watch has 4 LEDs on the top to represent the hours (0-11), and 6
 * LEDs on the bottom to represent the minutes (0-59). Each LED represents a
 * zero or one, with the least significant bit on the right.
 *
 *
 * For example, the below binary watch reads "4:51".
 *
 *
 *
 *
 * Given an integer turnedOn which represents the number of LEDs that are
 * currently on (ignoring the PM), return all possible times the watch could
 * represent. You may return the answer in any order.
 *
 * 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".
 *
 *
 *
 * Example 1:
 * Input: turnedOn = 1
 * Output:
 * ["0:01","0:02","0:04","0:08","0:16","0:32","1:00","2:00","4:00","8:00"]
 * Example 2:
 * Input: turnedOn = 9
 * Output: []
 *
 *
 * Constraints:
 *
 *
 * 0 <= turnedOn <= 10
 *
 *
 */

// @lc code=start
class Solution {
public:
    vector<string> readBinaryWatch(int turnedOn) {
        vector<int> hours = {1, 2, 4, 8}, minutes = {1, 2, 4, 8, 16, 32};
        vector<string> ans;
        string s;

        for(int hour = 0;hour<12;hour++){
            for(int min =0;min<60;min++){
                s ="";
                if(__builtin_popcount(hour) + __builtin_popcount(min) == turnedOn )
                {
                    s += to_string(hour) + ":";

                    if(min < 10)
                    {
                        s += "0";
                    }
                    s += to_string(min);
                    ans.push_back(s);
                }
            }
        }
        return ans;
    }
};
// @lc code=end