What are the types of array initialization in C++?

c The types of array initialization include: 1. Initialization of integer array; 2. Initialization of string; 3. Default initialization of array; 4. Heap initialization of array.

c The types of array initialization are:

1. Initialization of integer array - stack initialization

//默认初始化
int a[5] = {};    //[0, 0, 0, 0, 0]
//全部初始化为0
int a[5] = {0};    //[0, 0, 0, 0, 0]
//c++11新写法
int a[5]{};    //[0, 0, 0, 0, 0]
//注意，想要整型数组 全部初始化为1的时候不能粗暴的设置为 
int a[5] = {1};    //[1, 0, 0, 0, 0]
// 因为 数组初始化列表中的元素个数小于指定的数组长度时， 不足的元素以默认值填补。
//可以分别赋值
int a[5] = {1,1,1,1,1}; //[1,1,1,1,1]

2. String initialization-stack initialization

is basically the same as the integer initialization, and the constructor will be called

string *str = string[5];    //调用5次默认构造函数
string *str1 = string[5]{"aaa"};    //数组中的第一个元素调用 string::string(const char *)  进行初始化。后面四个调用 默认构造函数

3. Default initialization of arrays

If the initialization list is not explicitly pointed out, then the basic types will not be initialized (except global variables and static variables), and all memory will be dirty data; and automatically The defined class type will call the default constructor for each element for initialization

int a[5]{};
a[6];      //32766
a[10];    //1474921429
// Xcode会提示 Array index 10 is past the end of the array (which contains 5 elements)。虽然不会爆红，但是Xcode提示越界了。这在程序中也是需要特别注意的,越界时会取到脏数据。
string str[5];     //["","","","",""]
string str1[5] = {"","2","",""};     //["","2","',"",""]
string str2[5] = {"a"};     //["a","","","",""]

4. Heap initialization of the array

int *a = new int[5];        //脏数据数组
int *str = new string[5];    //空字符串数组
int *b = new int[5]{0};    //   [0,0,0,0,0]
int *str1 = new string[5] {"aaa"};    //["aaa","","","",""]
//以上几行代码遵循栈中数组的初始化规则，除此之外这里还有一个新语法
int *c = new int[5]();    //[0,0,0,0,0]
//该语法后面的一对圆括号，表示使用默认值初始化整个数组，所以对于类类型来说，new string[5] 与 new string[5]() 是等价的，都会调用默认构造函数进行初始化；但是对于基本类型就不同了。new int[5]根本不会初始化，而new int[5]()则会使用int()的值，即0进行初始化。

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