[SOLVED] Could someone explain how this function works? I've solved when I put the variable num as 5, but something is wrong.

Question

int recursive(int num) {
if (num == 1)
return 2;

return num * recursive(num-1);
}

Answer 1

For num = 5.

recursive ( 5 ) will return
5 * recursive ( 5 - 1)
= 5 * ( 4 * recursive (4-1) )
= 5 * 4 * ( 3 * recursive (3-1))
= 5 * 4 * 3 * ( 2 * recursive (2-1))
= 5 * 4 * 3 * 2 * 2 { as recursive (1) will return 2 }
= 240

So the final value returned by recursive (5) should be 240.

Answer 2

recursive(5)
num*recursive(4)
num*recursive(3)
num*recursive(2)
num*recursive(1).

recursive(1) returns 2

recursive(2) returns num*recursive(1) = num*2=2*2=4

recurisve(3) returns num*recursive(2) = num*4=3*4=12

recurisve(4) returns num*recursive(3) = num*12=4*12=48

revursive(5) returns num*recursive(4) =num*48=5*48=240

functions were pushed onto the stack and then popped off .

Refer to the following video if you want to see visualization for it .

https://youtu.be/AIwxbJ5mP8M

Answer 3

Thanks for effort! Arsenic

Answer 4

Thanks for effort! Abhay