Little Endian to Big Endian

Code

#include <stdio.h>
#include <stdint.h>

uint32_t convert_endian(uint32_t val) {
	// Only uses a single extra 32 bit value
    uint32_t temp = (val & 0x000000FF);
    val &= 0xFFFFFF00;
    val |= ((val & 0xFF000000) >> 24);
    val &= 0x00FFFFFF;
    val |= (temp << 24);
    temp = val & 0x0000FF00;
    val &= 0xFFFF00FF;
    val |= ((val & 0x00FF0000) >> 8);
    val &= 0xFF00FFFF;
    val |= (temp << 8);
    return val;
}

int main() {
    uint32_t val;
    scanf("%u", &val);
    printf("%u", convert_endian(val));
    return 0;
}

Solving Approach