190. Reverse Bits

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190. Reverse Bits

Description

Reverse bits of a given 32 bits unsigned integer.

Note:

  • 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:

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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:

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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** .

Constraints:

  • The input must be a binary string of length 32

Follow up: If this function is called many times, how would you optimize it?

Hints/Notes

  • 2024/12/31
  • bit manipulation
  • No solution from 0x3F

Solution

Language: C++

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class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        int m = 31;
        uint32_t res = 0;
        while (n) {
            int residue = n % 2;
            n /= 2;
            res += residue << m;
            m--;
        }
        return res;
    }
};