2.74 Sub OK

★★

Problem:

Write a function with the following prototype:

/* Determine whether arguments can be subtracted without overflow */
int tsub_ok(int x, int y);

This function should return 1 if the computation x-y does not overflow.

Code:

#include <stdio.h>
#include <assert.h>
#include <limits.h>

int tsub_ok(int x, int y) {
    int sub = x - y;
    int pos_flag = x >= 0 && y < 0 && sub < 0;
    int neg_flag = x < 0 && y >= 0 && sub >=0;
    return !pos_flag && !neg_flag;
}

int main() {
    assert(!tsub_ok(INT_MIN, 1));
    assert(!tsub_ok(INT_MAX, -1));
    assert(tsub_ok(0, 0));
    assert(!tsub_ok(INT_MIN, INT_MAX));
    assert(!tsub_ok(INT_MAX, INT_MIN));
    assert(tsub_ok(10, 8));
    return 0;
}