190. Reverse Bits

Reverse bits of a given 32 bits unsigned integer.

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.

Approach 1:

Bit manipulation

The approach is simple .We take the least significant bit in ‘n’ followed by right shifting it. The obtained bit is added at the corresponding position in the reversed form(This is done by adding the obtained bit at the LSB of the intermediated result followed by a left shift). At the end of the iteration we get the required answer in the reverse form

class Solution:
    def reverseBits(self, n: int) -> int:
        res=0
        for i in range(0,32):
            res<<=1
            res|=(n&1)
            n>>=1    
        return res

Time :O(1)

Space : O(1)