124. Detect Underflow in Unsigned Subtraction

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

void subtract_with_underflow(uint8_t a, uint8_t b, uint8_t *diff, uint8_t *carry) {
    uint16_t temp = (uint16_t)a - (uint16_t)b;

    *diff = (uint8_t)(temp & 0xFF);    // get lower 8 bits
    *carry = (a < b) ? 1 : 0;          // underflow (borrow) detection
}

int main() {
    uint8_t a, b, diff, carry;
    scanf("%hhu %hhu", &a, &b);
    subtract_with_underflow(a, b, &diff, &carry);
    printf("diff = %u, carry = %u\n", diff, carry);
    return 0;
}