Numbers with K set bits
Count the integers from 0 to N − 1 whose binary form has exactly K ones.
Reported in: Deloitte (memory-based)
Input
One line: N and K.
Output
The count.
Constraints
1 ≤ N ≤ 10^6; 0 ≤ K ≤ 20.
Example 1
Input:
7 2
Output:
3Example 2
Input:
16 1
Output:
4Hint: For small N, count the ones in each number with bin(x).count("1") or a bit loop.