[leetcode] 190. Reverse Bits _ Algorithm Problem Solve for python

1. Problem

190. Reverse Bits

Reverse bits of a given 32 bits unsigned integer.


  • Note that in some languages, such as Java, there is no unsigned integer type. In this case, both input and output will be given as a signed integer type. They should not affect your implementation, as the integer’s internal binary representation is the same, whether it is signed or unsigned.
  • In Java, the compiler represents the signed integers using 2’s complement notation. Therefore, in Example 2 above, the input represents the signed integer -3 and the output represents the signed integer -1073741825.

Example 1:

Input: n = 00000010100101000001111010011100
Output:    964176192 (00111001011110000010100101000000)
Explanation: The input binary string 00000010100101000001111010011100 represents the unsigned integer 43261596, so return 964176192 which its binary representation is 00111001011110000010100101000000.

Example 2:

Input: n = 11111111111111111111111111111101
Output:   3221225471 (10111111111111111111111111111111)
Explanation: The input binary string 11111111111111111111111111111101 represents the unsigned integer 4294967293, so return 3221225471 which its binary representation is 10111111111111111111111111111111.


  • The input must be a binary string of length 32

2. Solution

I solved this problem like this.

  • It is so easy!
  • I can use ‘{0:032b}’.format(n). It makes n to binary num.
  • And i use int(binary_string, 2), i can get int.
class Solution:
    def reverseBits(self, n: int) -> int:
        bi_num = '{0:032b}'.format(n)
        ans = int(bi_num[::-1], 2)
        return ans