动态分配内存--new、delete

C++中使用new/delete用来动态分配、回收内存空间。

#include<iostream>
using namespace std;
int main()
    {
        int * pi = new int;
        cout << (void*)pi << endl;
        *pi = 1234;
        cout << *pi << endl;
        delete pi;//删除pi的目标，pi是局部变量。释放内存
        cout << (void*)pi << endl;//变成野指针，但pi指向的地址并没有变化
        pi = NULL;//置空。

        ///////初始化

        pi = new int(100);
        cout << *pi << endl;
        delete pi;
        pi = NULL;
        
        ///////分配数组，无初值，用数组方式new的，必须以
        //数组方式(delete [])释放
        int i=0,j=0;
        pi = new int [10];
        for ( i = 0; i < 10 ; i++)
            pi[i] = i+1;
        for ( i = 0; i < 10 ; i++)
            cout << pi[i] << endl;
        cout << endl;
        delete [] pi;
        pi = NULL;

        ///初始化数组

        pi = new int[3]();//初始值为0
        for ( j = 0; j < 3; j++)
            cout << pi[j] << endl;
        delete [] pi;
        pi = NULL;

        //////////动态创建二维数组/////////

        int (*pa)[4] = new int [3][4]();//初始值为0，指针数组
        for (i = 0; i < 3; i++)
            for(j = 0; j < 4; j++)
                cout << pa[i][j] << endl;
            delete [] pa;
            pa = NULL;

        return 0;}