How this code works & the ans?

Question

int f(int *a, int n){
if(n<=0)
return 0;
else if(*a%2==0)
return *a + f(a+1, n-1);
else
return *a - f(a+1, n-1);
}
int main(){
int a[] = {12,7,5}
printf("%i", f(a,3));
}

Answer 1

You can't dereference 'a' argument because it is not a potiner.
maybe it should be:
int f(int *a, int n)
and not
int f(int *n, int a)?

If so then the function uses recursion to iterate over all array elements.
If current element is even (*a % 2 == 0) then result is the sum of the current element and the result of f() applied to remaining elements.
If current element is odd then result is the difference between the current element and the result of f() applied to remaining elements.

or step by step:

f(a, 3) = f({12, 7, 5}, 3)
*a is 12 it is even (*a % 2 is zero), so it returns sum:
return *a + f(a+1, n-1)

a+1 is move pointer to the next element (2nd) of the array, n-1 = 2 number of elements in the array:
return 12 + f({7, 5}, 2)

f({7, 5}, 2):
*a = 7 it is odd, so difference is calculated
return *a - f(a+1, n-1)
a+1 is moved pointer to the next element (3rd), n = 2 - 1 = 1
return 7 - f({5}, 1)

f({5}, 1):
*a = 5 it is odd, so difference is calculated:
return *a - f(a+1, n-1)
a+1 is moved pointer to the next element (out of bounds), n = 1 - 1 = 0
return 5 - f(ptr, 0)
as n<=0 the function returns 0 (it is base case)

so, as base case has been met execution in the caller continues:
f(ptr, 0) = 0
f({5}, 1) will return 5 - f(ptr, 0) = 5 - 0 = 5
f({7, 5}, 2) will return 7 - f({5}, 1) = 7 - 5 = 2
f({12, 7, 5}) will return 12 + f({7, 5}, 2) = 12 + 2 = 14

14 is the result of the function

Answer 2

This code has many errors ,I don't have knowledge in c or c++ ,lol you don't even know it's a c or c++? Anyway try to resolve those errors first and search why those * are used ,do some self learning that's the best way to understand them,then ask if you are facing any problem about specific things that you can't understand

Answer 3

andriy kan is correct .Very gud explaination.

Answer 4

Thank you andriy kan❤
I edited it..

Answer 5

I found it from sololearn challenge. I tried to understand this code & i failed, that's why i posted it. If you don’t know the answer, don’t need to say unnecessary things.
Thank you.
& i know It's a c language, c or c++, they are about to same, anyone who know the one, know the other one, so i add c & c++ too