C++ unordered_set insert insert PHP

Question

I have a code on C++ which I have to rewrite on PHP. Weird thing happens for me as I'm PHP programmer and don't know C++ well. This is the code:

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

int func(int choice) {

    unordered_set<int> hset;
    for (int counter = 0; counter < choice; counter++) {
        hset.insert(counter);
        if (counter % 2 == 0) {
            hset.insert(counter);
            hset.insert(counter + 1);
        }
    }
    return hset.size();
}

int main(int argc, char** argv) {
    cout << func(561);
    return 0;
}

Output of the code is: 562;

I have written PHP code like this:

function func($choice) {

$hset = [];

for ($counter = 0; $counter < $choice; $counter++) {
    array_push($hset, $counter);
    if ($counter % 2 == 0) {
        array_push($hset, $counter);
        array_push($hset, $counter + 1);
    }
}

    return count($hset);
}

echo func(561);

It returns 1123. Please help.

Answer 1

C++'s unordered_set will not allow duplicate elements. Since you are pushing counter and counter+1 in, you are generally trying to push the same element twice, and one of those times it gets rejected.

If you want to have similar behavior as PHP, use a std::vector instead, with emplace_back (or push_back) to add your elements.

If you want to go the other way, then in PHP you could use array_unique