Solution with 0(n), but with a while to clear the trash

main.cpp

#include <iostream>
using namespace std;

void writeOnConsole(int * array, int arraySize) {
    for (int i = 0; i < arraySize;i++)
      cout << array[i] << ", ";
    cout << array[arraySize] << endl;
}

int main() {
    int array[] = {3, 2, 0, 4, 8, 0, 5, 9, 0, 11, 0, 45, 0, 23, 21, 0, 36};
    int arraySize = sizeof(array)/sizeof(int) - 1;
    int write = arraySize;

    for (int read = arraySize; read >= 0; read--)
        if(array[read] == 0)
            continue;
        else
            array[write--] = array[read];

    // clear trash
    while ( write >= 0 ) {
        array[write] =0;
        write--;
    }

    writeOnConsole(array, arraySize);
    return 0;
}