Introduction

In this blog post, we will explore how to solve the LeetCode problem "190" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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: 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. 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?

Explanation

• Bit Manipulation: Utilize bitwise operators to efficiently reverse the bits. Iterate through the bits, swapping the i-th bit with the (31-i)-th bit.
  • Optimization with Caching (for Follow-up): Implement a cache (e.g., a dictionary or array) to store the reversed values of smaller chunks of bits (e.g., bytes or nibbles). This avoids redundant calculations when the function is called repeatedly with similar inputs.
  • 32-bit Unsigned Integer Handling: The problem statement specifies a 32-bit unsigned integer. This affects the range of values that can be represented, but not the bitwise operations themselves.

• Runtime Complexity: O(1) (since the number of iterations is fixed at 32)
• Storage Complexity: O(1) (excluding the optional caching for the follow-up, which would introduce O(n) where n is the size of the cache.)

Code

    def reverseBits(n: int) -> int:
    """
    Reverses the bits of a 32-bit unsigned integer.
    """
    result = 0
    for i in range(32):
        # Get the rightmost bit of n
        bit = (n >> i) & 1

        # Set the corresponding bit in result to the reversed position
        result |= (bit << (31 - i))

    return result