[Solved]List inserting

Question

I have a list of n integers. I'm trying to add after each even number it's double. Below is my try:

#include <iostream>
#include <list>
using namespace std;

int main() {
int n, x, aux;
cin >> n;
list<int> l;
for(int i = 0; i < n; i++){
cin >> x;
l.push_back(x);
}
list<int>::iterator it;
it = l.begin();
for( ; it != l.end(); ++it){
aux = *it;
if( aux % 2 == 0){
++it;
l.insert(it, aux * 2);
}
continue;
}
list<int>::iterator j;
for(j = l.begin(); j != l.end(); ++j)
cout << *j << " ";

return 0;
}

It works, but the doubles are added twice. I've tried to increase the iterator and the continue keyword but I've got the same results. How can I fix this?

Answer 1

If you want a simple fix, add

it--;

after

l.insert(it, aux*2);

Answer 2

I removed it and it inserts the doubled number before, but the problem I'm solving requires it to be after. Using list::unique seems to fix it. I'm still open to another way of solving this problem. Thanks for the response 🍪

Answer 3

Ok, thanks. I'll try iterating backwards and I'll post the result.

Answer 4

Hatsy Rei thanks, works like a charm!

Answer 5

I appreciate your help, feel free to do it when you have time.

Answer 6

SagaTheGreat it inserts the doubled number at the beginning of the list, but I needed it to be after the number.
Here's a cookie for your attempt: 🍪

Answer 7

Iterating through a list while adding elements to it can be tricky since it involves iterators re-adjusting themselves, and it's late here so I can't really handtrace it out for now.

Answer 8

I think ++it is the cause. If you remove that line then it should work fine.
Like below,
if( aux % 2 == 0)
{
l.insert(it, aux * 2);
}

Another solution is you can do like below;
if( aux % 2 == 0)
{
l.push_front(aux * 2);
}

Thanks,

Answer 9

Anime FanGirl Have you tried as I mentioned above?

it is working I have confirmed.

Answer 10

that's right!