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:
static public List<string> ReadBinaryWatch(int num) {List<string> list = new List<string>();string s = "";for (int i = 0; i < 12; i++) {for (int j = 0; j < 60; j++) {if (BitCount(i) + BitCount(j) == num) {list.Add(i.ToString() + ":" + NumberToString(j));}}}return list;}static public int BitCount(int number) {int sum = 0;while (number > 0) {if ((number & 1) == 1) {sum++;}number >>= 1;}return sum;}static public string NumberToString(int number) {string s = number.ToString();return s.PadLeft(2, ‘0‘);}
原文：http://www.cnblogs.com/xiejunzhao/p/9a2a5a9e740619d04df1af25c93e6204.html