Lintcode 1046. Prime Number of Set Bits in Binary Representation

1046. Prime Number of Set Bits in Binary Representation

Description

Given two integers L and R, find the count of numbers in the range [L, R] (inclusive) having a prime number of set bits in their binary representation.

(Recall that the number of set bits an integer has is the number of 1s present when written in binary. For example, 21 written in binary is 10101 which has 3 set bits. Also, 1 is not a prime.)

Example
Example 1:

Input: L = 6, R = 10
Output: 4
Explanation:
6 -> 110 (2 set bits, 2 is prime)
7 -> 111 (3 set bits, 3 is prime)
9 -> 1001 (2 set bits , 2 is prime)
10->1010 (2 set bits , 2 is prime)
Example 2:

Input: L = 10, R = 15
Output: 5
Explanation:
10 -> 1010 (2 set bits, 2 is prime)
11 -> 1011 (3 set bits, 3 is prime)
12 -> 1100 (2 set bits, 2 is prime)
13 -> 1101 (3 set bits, 3 is prime)
14 -> 1110 (3 set bits, 3 is prime)
15 -> 1111 (4 set bits, 4 is not prime)

Code

class Solution:
    """
    @param L: an integer
    @param R: an integer
    @return: the count of numbers in the range [L, R] having a prime number of set bits in their binary representation
    """
    def countPrimeSetBits(self, L, R):
        # Write your code here
        dict = {2,3,5,7,11,13,17,19,23,29,31}
        res = 0
        for i in range(L, R+1):
            if bin(i).count('1') in dict:
                res += 1
        return res