C++

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recursion

Minessota (8)
Why does this function count upwards and not downwards? Any help is appreciated thanks.

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#include <cstdio>
#include <cmath>

void f1(int x);

int main()
{
   f1(4);
}

void f1(int x)
{
   if(x > 0) {
      int newX = x - 1;
      f1(newX);
      printf("%d\n", newX);
   }
}
JLBorges (13770)
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#include <cstdio>
#include <cmath>

void f_upwards(int x) {

   if(x > 0) {

      int newX = x - 1;
      f_upwards(newX);
      std::printf("%d\n", newX); // print after the recursive call
   }
}

void f_downwards(int x) {

   if(x > 0) {

      int newX = x - 1;
      std::printf("%d\n", newX); // print before the recursive call
      f_downwards(newX);
   }
}

int main() {

   std::puts( "upwards: " ) ;
   f_upwards(4);

   std::puts( "\ndownwards: " ) ;
   f_downwards(4);
}
Minessota (8)
Why doesn't void f_upwards(int x) just loop until 0 then terminate?
JLBorges (13770)
f_upwards(4) calls f_upwards(3)
    f_upwards(3) calls f_upwards(2)
        f_upwards(2) calls f_upwards(1)
            f_upwards(1) calls f_upwards(0)
                f_upwards(0) does nothing and returns to f_upwards(1)
            f_upwards(1) prints 0 and returns to f_upwards(2)
        f_upwards(2) prints 1 and returns to f_upwards(3)
    f_upwards(3) prints 2 and returns to f_upwards(4)
f_upwards(4) prints 3 and returns to main()
Minessota (8)
Okay thank you!
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