Subtracting two numbers without using '-' operator

Question

i tried with the following code , but i can\'t understand why it\'s giving me wrong answer. i am computing the 2\'s complement and adding with another no.

#inclu         


        

Answer 1

You also can implement this recursively. In C this might look like:

#include 

int add(int a, int b){
    if(b == 0) return a;
    int sum = a ^ b;
    int carry = (a & b) << 1;
    return add(sum, carry);
}

int subtract(int a, int b){
    return add(a, add(~b, 1));
}

int main(){

    int a = 3;
    int b = 1;

    int sum = add(a, b);
    printf("%i + %i = %i \n", a, b, sum);

    int difference = subtract(a, b);
    printf("%i - %i = %i \n", a, b, difference);

    return 0;
}