5.4 Allocate memory: C style

Operator new and new[]
Operator new is similar with malloc() but with more features.

//allocate an int, default initializer (do nothing)
int * p1 = new int; 
//allocate an int, initialized to 0
int * p2 = new int();
//allocate an int, initialized to 5
int * p3 = new int(5); 
//allocate an int, initialized to 0
int * p4 = new int{};//C++11 
//allocate an int, initialized to 5
int * p5 = new int {5};//C++11
//allocate a Student object, default initializer
Student * ps1 = new Student;
//allocate a Student object, initialize the members
Student * ps2 = new Student {"Yu", 2020, 1}; //C++11

//allocate 16 int, default initializer (do nothing) 
int * pa1 = new int[16];

//allocate 16 int, zero initialized 
int * pa2 = new int[16]();

//allocate 16 int, zero initialized 
int * pa3 = new int[16]{}; //C++11

//allocate 16 int, the first 3 element are initialized to 1,2,3, the rest 0
int * pa4 = new int[16]{1,2,3}; //C++11

//allocate memory for 16 Student objects, default initializer
Student * psa1 = new Student[16];

//allocate memory for 16 Student objects, the first two are explicitly initialized
Student * psa2 = new Student[16]{{"Li", 2000,1}, {"Yu", 2001,1}}; //C++11

Operator delete and delete[]
Destroys object/objects allocated by new and free memory

//deallocate memory
delete p1;
//deallocate memory
delete ps1;

//deallocate the memory of the array
delete pa1;
//deallocate the memory of the array
delete []pa2;
// 8 == 10

//deallocate the memory of the array, and call the destructor of the first element
delete psa1;
//deallocate the memory of the array, and call the destructors of all the elements
delete []psa2;
// 释放所有内存，只会把第一个元素的析构函数，17行代码会调用所有元素的析构函数