DevHeads IoT Integration Server•11mo ago

Swap Odd and Even Bits

Write a C function to swap all odd and even bits in an unsigned integer. Bit positions 0, 2, 4, ... are considered even bits, and positions 1, 3, 5, ... are odd bits. Ex input: 10101010 (in binary), Expected O/P: 01010101. It may look simple at first, well, like just outputting its complement, but is that right? What if the input is 11010010? How would you proceed with this question?

2 Replies

brotherjoons•11mo ago

Complement works, right? Ah, but you have to limit the length of the values to be complemented. (& 0xff, etc...)

nour_oud•11mo ago

C 
C 
#include <stdio.h>

unsigned int swapOddEvenBits(unsigned int num) {
    // Masks for even and odd bits
    unsigned int evenMask = 0b10101010101010101010101010101010;
    unsigned int oddMask = 0b01010101010101010101010101010101;

    // Extract even and odd bits
    unsigned int evenBits = num & evenMask;
    unsigned int oddBits = num & oddMask;

    // Swap even and odd bits
    evenBits >>= 1;
    oddBits <<= 1;

    // Combine swapped even and odd bits
    return evenBits | oddBits;
}

int main() {
    // Example input: 10101010 
    unsigned int num = 0b10101010;

    // Print input
    printf("Input:  %08x\n", num);

    // Swap odd and even bits
    unsigned int result = swapOddEvenBits(num);

    // Print output
    printf("Output: %08x\n", result);

    return 0;
}

C 
C 
#include <stdio.h>

unsigned int swapOddEvenBits(unsigned int num) {
    // Masks for even and odd bits
    unsigned int evenMask = 0b10101010101010101010101010101010;
    unsigned int oddMask = 0b01010101010101010101010101010101;

    // Extract even and odd bits
    unsigned int evenBits = num & evenMask;
    unsigned int oddBits = num & oddMask;

    // Swap even and odd bits
    evenBits >>= 1;
    oddBits <<= 1;

    // Combine swapped even and odd bits
    return evenBits | oddBits;
}

int main() {
    // Example input: 10101010 
    unsigned int num = 0b10101010;

    // Print input
    printf("Input:  %08x\n", num);

    // Swap odd and even bits
    unsigned int result = swapOddEvenBits(num);

    // Print output
    printf("Output: %08x\n", result);

    return 0;
}

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Swap Odd and Even Bits