C++-new动态变量申请 delete 删除动量地址

/*
new动量申请
*/ 
#include <iostream>

using namespace std; 

int main() {
    int *pi = new int; 
    *pi = 10; 
    cout << *pi << endl; 
    delete pi; 
    pi = NULL; 

    int *pi2 = new int(20); 
    cout << *pi2 << endl;
    (*pi2)++;
    cout << *pi2 << endl; //21 
    delete pi2; 
    pi2 = NULL; 
}

/*
使用new构造arr
*/
#include <iostream>

using namespace std; 

int main(void) {
    int* p_arr = new int[10]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; 
    for (int i = 0; i < 10; i++) {
        cout << *(p_arr + i) << endl; 
    }
    delete[] p_arr; 
    p_arr = NULL; 
    return 0;  

}

/*
delete 
*/ 

#include <iostream>

using namespace std; 

int main(void) {
    //int *pi; //需要进行赋值以后再进行删除 
    //delete pi; //容易变成野指针 

    int *pi2 = NULL; 
    delete pi2; //可以正常使用 
    

    int *pi3 = new int; 
    delete pi3; 
    pi3 = NULL; 
    //     
    //容易出现二级指针定义失误
    return 0;   
}