Little Endian to Big Endian

Code

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

#define MASK1(value)        (value & (0x000000FF))
#define MASK2(value)        (value & (0x0000FF00))
#define MASK3(value)        (value & (0x00FF0000))
#define MASK4(value)        (value & (0xFF000000))        

uint32_t convert_endian(uint32_t value) {
    // Write logic to swap bytes

    uint32_t result = 0;

    result = (MASK1(value) << 24) | (MASK2(value) << 8) + (MASK3(value) >> 8) + (MASK4(value) >> 24);

    return result;
}

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

Solving Approach

/*
Swap bytes problem in disguise

Example 1:
Input: 305419896
Output: 2018915346

0x12_34_56_78 -> 0x78_56_34_12

78
56
34
12

Plan:
- extract each byte using masks
- move the bytes to the required position using right shift
- return the result


Mask 1: 0x00_00_00_FF 
Mask 2: 0x00_00_FF_00
Mask 3: 0x00_FF_00_00 
Mask 4: 0xFF_00_00_00 

1st byte will be shifted to the left by 24
2nd byte by 8
3rd byte to right by 8
4th byte shift to right by 24

*/