Can someone explain this recursive to me?

Question

#include<stdio.h>
#include<stdlib.h>

int recurse(int n);

int main(){

printf("%d",recurse(5));
return 0;
}

int recurse(int n){

if(n<=1)
return 20;
return(2+recurse(n-1));

}

Answer 1

Mik_RDC

recurse(5)
2 + recurse(4)
2 + 2 + recurse(3)
2 + 2 + 2 + recurse(2)
2 + 2 + 2 + 2 + recurse(1)
2 + 2 + 2 + 2 + 20
= 28

Answer 2

Mik_RDC

Working process will be same just value will be change based on (n - 1)

5 + recurse(4)
5 + 4 + recurse (3)
5 + 4 + 3 + recurse (2)
5 + 4 + 3 + 2 + recurse (1)
5 + 4 + 3 + 2 + 20
= 34

Answer 3

Thank you Mr AJ
But if the last line was:

return(n+recuse(n-1));

Program will work the same or change ?

Answer 4

the stdlib is unused.

we have a recursive function, it takes an int, and returns an int.

we give it five, it will keep calling itself if the input is greater than one. (the base case / end of recursion).

if the input is 1 or less, it will return 20.

if the input is greater than 1, it will return 2 plus calling itself with the same input minus 1.

--------------------------------

print(r(5))

r(5) + r(4) + r(3) + r(2) + 20
2 + 2 + 2 + 2 + 20

output:
28

Answer 5

if the input is 1 or less it will just return 20 (base case to end the Recursion).

you can use any number like 0, 1, 40, any number as you need.

Answer 6

Thank to all help me

Answer 7

It will become
5 + 4 + 3 + 2 + 20
= 34

Answer 8

G'day Mik_RDC that 20 at the end is strange.

It must be part of the aim of the program, eg each person costs $2 and the first person in the taxi costs $20.

Answer 9

Mik_RDC

20 at the end because on (n <= 1) function will return 20 so this is not a strange thing.

When n is 0 then else will not execute so further execution will stop there and final result will be print

Answer 10

Waiting your help...

Answer 11

I know factorial , but this recurse complicated me sure , am fixed twenty why 20 in last

Answer 12

normally the recursive decreases the number but here there is a 20 at the end

Answer 13

recurse(5)
2 + recurse(4)
2 + 2 + recurse(3)
2 + 2 + 2 + recurse(2)
2 + 2 + 2 + 2 + recurse(1)
2 + 2 + 2 + 2 + 20 // base condition start work and return back control
= 28