Extract Even Bits Only from 32-bit Register

Code

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

uint32_t extract_even_bits(uint32_t reg) {
    // Your code here
    uint32_t result = 0,flag = 0;
    int i,j;
    uint32_t data_type_size = sizeof(reg) * 8;
    for( i=0,j=0; i<data_type_size; i=i+2)
    {
        flag = (reg >> i) & 1; // 0000 1111 & 1<<0
        result = result | flag << j;
        j++;
    }
    return result;
}

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

Solving Approach