memory problems

badfree.cpp

#define size 30
#include <cstdlib>
void allocate_array(int** array) { *array = new int[size]; }
int main() {
    int* array;
    allocate_array(&array);
    int count;
    for (count = 0; count < size; ++count) {
        array[count] = count;
    }
    delete array;
    return EXIT_SUCCESS;
}

nofree.cpp

#define size 30
#include <cstdlib>
void allocate_array(int** array) { *array = new int[size]; }
int main() {
    int* array;
    allocate_array(&array);
    int count;
    for (count = 0; count < size; ++count) {
        array[count] = count;
    }
    // delete array;
    return EXIT_SUCCESS;
}

vecoverflow.cpp

#include <cstdlib>
#include <iostream>
#include <vector>
#define size 6
int main() {
    std::vector<int> ints{1, 2, 5, 7, 9};
    for (int count = 0; count < size; ++count) {
        std::cout << ints[count] << std::endl;
    }
    return EXIT_SUCCESS;
}

vecuninit.cpp

#include <iostream>
#include <vector>
#include <cstdlib>
const int size = 3;
int main() {
    int array[size];
    std::cout << array[0] << std::endl;
    return EXIT_SUCCESS;
}