Range Bit Counting

Task

You are given two numbers a and b where 0 ≤ a ≤ b. Imagine you construct an array of all the integers from a to b inclusive. You need to count the number of 1s in the binary representations of all the numbers in the array.

Example

For a = 2 and b = 7, the output should be 11

Given a = 2 and b = 7 the array is: [2, 3, 4, 5, 6, 7]. Converting the numbers to binary, we get [10, 11, 100, 101, 110, 111], which contains 1 + 2 + 1 + 2 + 2 + 3 = 11 1s.

Input/Output

• [input] integer a

Constraints: 0 ≤ a ≤ b.

• [input] integer b

Constraints: a ≤ b ≤ 100.

• [output] an integer

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def range_bit_count(a, b):
    ans=0
    for i in range(a,b+1):
        ans+=format(i,'b').count('1')
    return ans