Recursive function that divides two numbers, using successive subtraction

Question

I have tried but failed to do so. Could I have a push in the right direction?

Answer 1

Pseudocode only, since it's probably homework:

def div(a,b):
    if a < b return 0
    return div(a-b,b) + 1

Will only work for positive numbers, fixing it for negatives and divide-by-zero is left as an exercise.

It works by repeatedly subtracting b from a, and going down a level, until you can no longer subtract b from a without going negative. Then it returns up the recursion tree, adding 1 for each level you went down.

Some hints for handling signs and errors:

• Detect straight up if b is equal to zero and exit with an error.
• -a/-b is the same as a/b.
• -a/b is the same as -(a/b).
• a/-b is also the same as -(a/b).
• those four special cases can be handled when first entering the div function, the final three can also be done by just adding some if statements and one recursion level.

Answer 2

#include <stdio.h>

int div(int a, int b){
int c;
c=a-b;
if(c<=0){
return 1;
}else{
return div(c, b) + 1;
}
}

int main(void){
printf("%d", div(12, 4));
return 0;
}

This works
http://codepad.org/iWhmbUua