An example program demonstrating time efficiency of different number-swapping algorithms

swap_numbers.c

#include <stdio.h>
#include <time.h>
#include <inttypes.h>

typedef struct {
    void (*function) (uint32_t *a, uint32_t *b);
    char *description;
} swapping_method;

void swap_temp(uint32_t *a, uint32_t *b) {
    uint32_t c = *a;
    *a = *b;
    *b = c;
}

void swap_pointers(uint32_t *a, uint32_t *b) {
    uint32_t *c = a;
    a = b;
    b = c;
}

void swap_sum(uint32_t *a, uint32_t *b) {
    *a += *b;
    *b = *a - *b;
    *a -= *b;
}

void swap_xor(uint32_t *a, uint32_t *b) {
    *a ^= *b;
    *b ^= *a;
    *a ^= *b;
}

swapping_method methods[] = {
    {
        .function = swap_temp,
        .description = "temporary integer"
    },
    {
        .function = swap_pointers,
        .description = "temporary pointer"
    },
    {
        .function = swap_sum,
        .description = "sum and difference"
    },
    {
        .function = swap_xor,
        .description = "XOR"
    }
};

int main() {
    for (int i = 0; i < sizeof(methods) / sizeof (swapping_method); i++) {
        uint32_t a = 0, b = 1;
        swapping_method method = methods[i];

        clock_t start = clock();

        for (int n = 0; n < 600000000; n++) {
            method.function(&a, &b);
        }

        clock_t end = clock();

        printf("Swapping integers using %s takes %f s\n", method.description,
            (float) (end - start) / CLOCKS_PER_SEC);
    }

    return 0;
}