338. Counting Bits, 338 countingbits

338. Counting Bits, 338 countingbits

Given a non negative integer number num. For every numbers I in the range 0 ≤ I ≤ num calculate the number of 1's in their binary representation and return them as an array.

Example:
Fornum = 5You shoshould return[0,1,1,2,1,2].

Follow up:

It is very easy to come up with a solution with run time O (n * sizeof (integer )). but can you do it in linear time O (n)/possibly in a single pass?

Space complexity shocould be O (n ).

Can you do it like a boss? Do it without using any builtin function like _ builtin_popcount in c ++ or in any other language

 

 1 /** 2  * Return an array of size *returnSize. 3  * Note: The returned array must be malloced, assume caller calls free(). 4  */ 5 int* countBits(int num, int* returnSize) { 6     int *ary; 7     int i; 8     int k; 9     ary = (int *)malloc((num + 1) * sizeof(int));10     for(i = 0; i <= num; i++)11     {12         ary[i] = 0;13         k = i;14         while(k)15         {16             k &= (k-1);17             ary[i]++;18         }19     }20     *returnSize = num + 1;21     return ary;22 }