I'm having trouble understanding recursive functions?

[3UMLy60M]

Hello all,

Can someone please explain to me how calling m3(3, 4) causes 81 to be the output of the following recursive function?

int m3 (int a, int b)
{
    if (b == 0)
        return 1;
    else
        return a * m3(a, b - 1);
}

And also, why is the output here 12 when m2(3, 4) is called?

int m2(int a, int b)
{
    if (a == 0)
        return 0;
    else
        return b + m2(a - 1, b);
}

Thanks!

[Peter87]

m3(3, 4) will return 3 * m3(3, 3),
m3(3, 3) will return 3 * m3(3, 2),
m3(3, 2) will return 3 * m3(3, 1),
m3(3, 1) will return 3 * m3(3, 0) and
m3(3, 0) will return 1,
so in other words m3(3, 4) will return 3 * (3 * (3 * (3 * 1))) = 81.

[Nobun]

analyze your own code ;)

m3 (3,4) = 3 * (3,3) = 3 * 3 * (3,2) = 3 * 3 * 3 * (3,1) = 3 * 3 * 3 * 3 * (3,0) = 3 * 3 * 3* 3 * 1 = 81

m2(3,4) = 4 + (2,4) = 4 + 4+ (1,4) = 4 + 4 + 4 + (0,4) = 4 + 4 + 4 + 0 = 12

[vlad from moscow]

Why are you duplicating your post in two section of the forum? Do not do that.