+ 9

# Why the output of this code is 012345, but not 543210?

#include <stdio.h> int main() { int loopy(int i){ if(i==0){ printf("%i",i); } else{ loopy(i-1); printf("%d",i); } } loopy(5); return 0; }

20th Jan 2019, 2:57 PM
Zhenis Otarbay
+ 5
Hello, How are you? Well, the problem is that you are using recursion. For example, considering i = 5, it will happen: "i == 0? No, so the else staments will be proccessed. The first stament is loopy(i-1). It will call the function again. Calling the function again, my i is 4, because 5 - 1 is equals 4. Now the same thing will happen, 4 == 0? No! So the else staments will processed and the first line is loopy(i-1). It will repeat with i = 3, 2 and 1. When i be equals 0, it will print. After it, all called functions of loopy will be finished by stack order (last in first out), in other words, the last else stament (print("%d", i)) following 1, 2 , 3 , 4 and 5". Well, it is happening. I am sorry because I didn't get to explain it clairly, but the problem is the recursion.
20th Jan 2019, 3:11 PM
Gabriel Felix dos Santos
+ 6
Just a little additional note to what Gabriel said, move the "loopy" function outside the main function, but first you follow his suggestion before you move it : )
20th Jan 2019, 4:34 PM
Ipang
+ 6
This is an interesting 5-question challenge quiz. Just like what Gabriel has explained, the reason output is 012345 is because the recursive is before print index. Therefore the whole logic is like a nested if else statement. If 5 is 0 __print 0 Else __if 4 is 0 ____print 0 __else ____if 3 is 0 ______print 0 ____else ______if 2 is 0 ________print 0 ______else ________if 1 is 0 __________print 0 ________else __________if 0 is 0 ____________print 0 __________else ____________... __________print 1 ________print 2 ______print 3 ____print 4 __print 5
20th Jan 2019, 4:57 PM
Gordon
+ 2
So, for your code prints what you would like, just you change the first and second else staments of place, such as: int loopy(int i) { if (i == 0) { printf("%i", i); } else { printf("%i, i); loopy(i - 1); } }
20th Jan 2019, 3:13 PM
Gabriel Felix dos Santos