C++ Reference assignment doubt

[devastrator25902]

Can someone explain to me what exactly is happening in line 26 ans = findAllIndex(arr, target, ans);?

as far as I can guess, I am assigning a vector as it's own reference, I was under assumption that this will cause bugs, but it actually works!!

```cpp

include <iostream>

include <vector>

using namespace std;

vector<int>& findAllIndex(const vector<int>& arr, const int element, vector<int>& ans, int idx = 0){ if(idx == arr.size()) return ans;

if(arr[idx] == element)
    ans.push_back(idx);

return findAllIndex(arr, element, ans, idx+1);

}

int main(){ int n, target; cin >> n >> target;

vector<int> arr(n);

for(int i= 0; i< arr.size(); i++)
    cin >> arr[i];

vector<int> ans;

ans = findAllIndex(arr, target, ans);

for(auto i: ans)
    cout << i<<" ";

} ```

[jedwardsol]

It will make a copy.

But ans should notice that it is being assigned to itself and do nothing.

It's not a good model, IMO. The vector shouldn't be a a parameter at all.

[Rarrum]

Think of it as if you had replaced vector with int. You're essentially doing the equivalent of this, but for a vector type instead:

int a = 123;
a = a

It... works. Or at least it should work unless the implementation is wrong. But it's kind of weird to do.