How do I randomly create and then fill a linked list with 20 elements containing 3 distinct objects, and then use a while loop to delete the old list and create a new one?

#include <iostream>
#include <list>
#include <stdlib.h>

using namespace std;

class shape
{
    public:
        shape(){}
        virtual ~shape(){cout<<"boom\n";}
        virtual char *getType() = 0;     
    private:
};

class circle : public shape
{
    public:
        char *getType() {return "circle";}
};

class square : public shape
{
    public:
        char *getType() {return "square";}
};

class triangle : public shape
{
    public:
        char *getType() {return "triangle";}
};


typedef list<shape*> shapeList_t;
typedef shapeList_t::iterator shapeListIter_t;

int main()
{
    int i, numItems=10;
    shapeList_t myList;
    shapeListIter_t myIter;
    shape *curShape;

    // Insert
    for (i=0; i<numItems; i++)
    {
        switch (rand() %  3)
        {
            case 0: myList.push_back(new circle); break;
            case 1: myList.push_back(new square); break;
            case 2: myList.push_back(new triangle); break;
        }
    }

    // Display
    for (myIter=myList.begin(); myIter!=myList.end(); myIter++)
    {
        curShape = *myIter;
        cout << "Shape type: " << curShape->getType() << endl;
    }

    // Cleanup
    for (myIter=myList.begin(); myIter!=myList.end(); myIter++)
    {
        curShape = *myIter;
        delete curShape;        // free the memory that this list item consumes - calls curShape's destructor
    }
    myList.clear();             // free the memory that the list uses to point to each list item - empties the list

    return 0;
}