Recursive C++ code goes into infinite loop

Question

Why does the following code go into an infinite loop:

#include<iostream>
using namespace std;

void printarray(int arr[], int n, int i);

int main(){
    int arr[] = {1,2,3,4,5};
    int n = sizeof(arr)/sizeof(arr[0]);
    printarray(arr,n,0);
    return 0;
}

void printarray(int arr[], int n, int i){
    if(i >=n)
        return;
    cout<<arr[i]<<"\t";
    return printarray(arr,n,i++);    //Replacing i++ by i+1 works fine
}

However, if I use i+1 instead of i++, the code works fine.As per my understanding i++ is effectively the same as i+1. Then what is the problem here?

`As per my understanding i++ is effectively the same as i+1` What would make you think so? — dxiv, May 01 '20 at 23:58

Ripi2 · Accepted Answer · 2020-05-02T00:08:04.493

2

i++ means "increment i after the comand finishes"

So you call the recursive function with always the same i. Only when the function returns iis incremented.

To achieve your goal use ++i instead.
Or better, as @dxiv pointed out, i+1

edited May 02 '20 at 00:08

answered May 02 '20 at 00:02

Ripi2

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Or just plain `i + 1`. The calling function returns right after the recursive call, so there is no real purpose to increment `i` at that point. – dxiv May 02 '20 at 00:04
@dxiv You're absolutely right. – Ripi2 May 02 '20 at 00:05
@dxiv Got it now. I was quite silly. Thank you guys – yksolanki9 May 02 '20 at 00:12

score 0 · Answer 2 · edited May 02 '20 at 04:19

0

I think you should put ++i instead of i++

edited May 02 '20 at 04:19

Mickael B.

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answered May 02 '20 at 00:00

Ibrahim Yesilay

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Recursive C++ code goes into infinite loop

2 Answers2