#include <iostream>
using namespace std;

int main() {

    cout << "----- Variable memory allocation -----" << endl;
    // 基础变量的内存分配
    // 初始化为 null 的指针
    double * pvalue  = NULL;

    // 为变量请求内存
    if(!(pvalue  = new double)) { 

        // 如果自由存储区已被用完，可能无法成功分配内存。
        cout << "Error: out of memory." <<endl;
        exit(1);

    }

    // 在分配的地址存储值
    *pvalue = 29494.99;
    cout << "Value of pvalue : " << *pvalue << endl;

    // 释放 pvalue 所指向的内存
    delete pvalue;

    cout << "----- 2D array memory allocation -----" << endl;
    // 二维数组的内存分配
    int ROW = 2;
    int COL = 3;
    
    // 为行分配内存
    double ** p2dArray  = new double * [ROW];
    double ** currRowPtr;
    double * currColPtr;

    // 为列分配内存
    for(int i = 0; i < ROW; i++) {

        p2dArray[i] = new double[COL];

    }

    // 指向起始位置
    currRowPtr = p2dArray;
    // 循环行
    for (int i = 0; i < ROW; i++) {

        cout << "Pointer of row[" << i << "] is: [";
        cout << *currRowPtr << "] at [" << currRowPtr << "]" << endl;

        // 循环列
        currColPtr = *currRowPtr;
        for (int j = 0; j < COL; j++) {

            cout << "Pointer of col[" << j << "] is: [";
            cout << *currColPtr << "] at [" << currColPtr << "]" << endl;

            currColPtr++;

        }

        currRowPtr++;

    }

    // 释放内存，释放的时候，需要确保指针指向的位置是已经被分配过的
    // 否则会出异常pointer being freed was not allocate
    // delete * p2dArray;
    // delete * currRowPtr;
    // delete currColPtr;

    cout << "----- Object memory allocation -----" << endl;
    // 对象的内存分配
    class Box {

        public:

            Box() {

                cout << "调用构造函数！" <<endl;

            }

            ~Box() {

                cout << "调用析构函数！" <<endl;

            }

    };

    Box * myBoxArray = new Box[4]; //
    Box * currBox = myBoxArray;

    for (int i = 0; i < 4; i++) {

        cout << "Pointer of myBoxArray[" << i << "] at [" << currBox << "]" << endl;
        currBox++;

    }

    delete [] myBoxArray;

}