code-bitmask-approach.cpp

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 *
 * Code for the book "DAILY 43: Algorithmic Problems for Coding Interviews: Easy level, C++ edition"
 *
 * Licensed under the GNU General Public License, Version 3.0 (the "License");
 * you may not use this file except in compliance with the License.
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#include <iostream>
#include <cstdint>
#include <bitset>

uint32_t reverseBits(uint32_t n) {
    n = (n >> 16) | (n << 16);
    n = ((n & 0xff00ff00) >> 8) | ((n & 0x00ff00ff) << 8);
    n = ((n & 0xf0f0f0f0) >> 4) | ((n & 0x0f0f0f0f) << 4);
    n = ((n & 0xcccccccc) >> 2) | ((n & 0x33333333) << 2);
    n = ((n & 0xaaaaaaaa) >> 1) | ((n & 0x55555555) << 1);
    return n;
}

int main() {
    uint32_t num = 43261596; // Example input (binary: 00000010100101000001111010011100)
    uint32_t reversed = reverseBits(num);
    std::cout << "Original: " << num << " (" << std::bitset<32>(num) << ")" << std::endl;
    std::cout << "Reversed: " << reversed << " (" << std::bitset<32>(reversed) << ")" << std::endl;

    return 0;
}