[LeetCode]401. Binary Watch

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本文介绍了一种算法，用于解析二进制手表显示的时间。通过输入点亮的LED数量，返回所有可能的时间表示。该算法利用预定义的小时和分钟组合，高效地生成结果。

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Easy

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”.

2ms:

 public List<String> readBinaryWatch(int num) {
         String[][] hour = {{"0"},
                            {"1","2","4","8"},
                            {"3","5","6","9","10"},
                            {"7","11"}};
         String[][] minute = {{"00"},//0
                            {"01","02","04","08","16","32"},//1
                            {"03","05","06","09","10","12","17","18","20","24","33","34","36","40","48"},//2
                            {"07","11","13","14","19","21","22","25","26","28","35","37","38","41","42","44","49","50","52","56"},//3
                            {"15","23","27","29","30","39","43","45","46","51","53","54","57","58"},//4
                            {"31","47","55","59"}//5
                            };
         List<String> result = new ArrayList<String>();
         for(int i=0;i<=num&&i<hour.length;i++){
             if((num-i)>=minute.length)
                 continue;
             String[] h_ = hour[i];
             String[] m_ = minute[num-i];
             for(int j=0;j<h_.length;j++){
                 for(int k=0;k<m_.length;k++){
                     result.add(h_[j]+":"+m_[k]);
                 }
             }
         }
         return result;
     }