leetcode 401. 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".
AC:
/**
* Return an array of size *returnSize.
* Note: The returned array must be malloced, assume caller calls free().
*/
int countOne(int k)
{
int len=0;
while(k>0)
{
if(k%2==1)
{
len++;
}
k=k/2;
}
return len;
}
char** readBinaryWatch(int num, int* returnSize) {
int h,m,len=0;
char** result=(char**)malloc(12*60*sizeof(char*));
for(h=0;h<12;h++)
{
for(m=0;m<60;m++)
{
if(countOne(h*64+m)==num)
{
result[len]=(char*)malloc(6*sizeof(char));
char buf[6];
sprintf(buf,"%d",h);
strcat(result[len],buf);
strcat(result[len],":");
if(m/10==0)
{
strcat(result[len],"0");
}
sprintf(buf,"%d",m);
strcat(result[len],buf);
len++;
}
}
}
*returnSize=len;
return result;
}