Question

How to reverse the bits of a number in C++

Answer 1

#include <iostream>
#include <bitset>
 
void print_bits(unsigned int n) { 
    std::bitset<32> bits(n);
    std::cout << bits << '\n';
}
 
unsigned int reverseBits(unsigned int num) {
    unsigned int total_bits = sizeof(num) * 8;
    unsigned int reversed_bits = 0;
 
    for (unsigned int i = 0; i < total_bits; i++) {
        if ((num & (1 << i))) {
            reversed_bits |= 1 << ((total_bits - 1) - i);
        }
    }
 
    return reversed_bits;
}
 
int main()
{
    unsigned int num = 42;
    print_bits(num);
    num = reverseBits(num);
    print_bits(num);
    std::cout << "\n";
     
    num = 19;
    print_bits(num);
    num = reverseBits(num);
    print_bits(num);
     
    return 0;
}
 
 
 
 
/*
run:
 
00000000000000000000000000101010
01010100000000000000000000000000
 
00000000000000000000000000010011
11001000000000000000000000000000
 
*/

 

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