Help with recursive multiplication table

[cdm545]

Hey there. I am a beginning c++ programmer and had a few questions on a program i wrote.

#include <iostream>
int mult(int n, int a, int b, int tab[5][5]){
	if( a == 0 && b <= n) {
		tab[a][b] = b;
		std::cout<< tab[a][b];
		return mult(n, a, b+1, tab);
	}
	else if( b == 0){
		tab[a][b] = a;
		std::cout << tab[a][b];
		return mult(n, a, b + 1, tab);
	}
	
	 else if(b <= n){
		tab[a][b] = a * b;
		std::cout<<tab[a][b];
		return mult(n, a, b + 1, tab);
	}
	else if (a <= n){
		b = 0;
		std::cout <<std::endl;
		return mult(n, a+1, b, tab );
	}
	else{
	return 0;
	}
		
}

int main(){
	unsigned int n = 5;
	int a =0, b = 0;
	int tab[5][5] = {};
	mult(n, a, b, tab);
}

The code complies and runs as it should but at the end it will tell me segmentation fault. I was wondering why. Also, how could I set the array to a user entered size? Thanks.

[L B]

On lines 3, 14, and 19, you accidentally used <= n instead of < n.

For arrays of user-defined size, I recommend you look into std::vector. You will want a vector of vectors.

[cdm545]

thanks! that worked perfectly. do you know of anyway to do it other than using vectors? My teacher is really picky on what we use and we can not use std::vector or std::string.

[L B]

If you are required to do it the deprecated way, you can do it like this:

unsigned xsize, ysize;
std::cin >> xsize >> ysize;
int **tab = new int*[xsize];
for(unsigned i = 0; i < xsize; ++i)
{
    tab[i] = new int[ysize];
}

int mult(int n, int a, int b, int **tab)
{
    //...
}

[cdm545]

Thanks!