c++stl和std_C ++ STL数组容器– std :: array

女爷i 2022-12-07 13:55 160阅读 0赞

![7cb3a601c4bf448d05a623805a35b8d8.png][]

c++stl和std

Here you will learn about STL Array Container in C++ i.e. std::array.

在这里，您将了解C ++中的STL数组容器，即std :: array。

I Hope you know about C-type arrays (arrays in C language). Since C++ is just extension to C language we can use those. The main property is that, Array contains series of elements of same type placed in contiguous memory locations. i.e suppose we have marks of 100 students, instead of declaring 100 variables, using array the 100 int values can store in contiguous memory locations and all can be accessed through same identifier, by just adding some number to identifier which points to particular index.

我希望您了解C型数组(C语言数组)。 由于C ++只是C语言的扩展，因此我们可以使用它们。 主要特性是，Array包含一系列放置在连续内存位置中的相同类型的元素。 也就是说，假设我们有100个学生的分数，而不是声明100个变量，而是使用数组将100个int值存储在连续的内存位置中，并且可以通过在标识符上添加一些数字(指向特定索引)来通过相同的标识符进行访问。

**Declaring Normal Array**

**声明法线数组**

**Syntax:** type arrayName\[size\];

**语法：**类型arrayName \[size\];

**Example:** int marks\[5\];  //This is array of type int which stores marks of 5 students

**示例：** int标记\[5\]； //这是int类型的数组，其中存储5个学生的分数

**Initializing Arrays**

**初始化数组**

int marks \[5\] = \{ 10, 23, 15, 20, 25 \};

整数标记\[5\] = \{10，23，15，20，25\};

This stores the elements in contiguous locations, that in index 0, element 10 will be stored remaining follows as same.

这会将元素存储在连续的位置，即在索引0中将存储元素10，其余部分相同。

**Accessing** **the** **elements** **of** **the** **array**:

**访问** **数组** **的** **元素** ：

**Syntax:** arrayName\[index\];

**语法：** arrayName \[index\];

**Example:** marks\[2\]; //This will gives the value of the element at 2nd index of the array marks, which is 15.

**示例：** marks \[2\]; //这将在数组标记的第二个索引处给出元素的值，即15。

If we try to access giving a number which is greater than size of the array in place of index, it will raise an error called arrayIndexOutof bound error.

如果我们尝试访问给定的数字，该数字大于数组的大小(而不是索引的位置)，它将引发一个名为arrayIndexOutof的错误。

These are directly implemented as a language feature, inherited form C language. They probably suffer from an excess of optimization. Very less inbuilt functions.

它们直接作为语言功能实现，继承自C语言。 他们可能遭受过多的优化。 内置函数很少。

## **C ++ STL数组** **(****C++ STL Array****)** ##

To overcome issues with language built-in arrays, [**C++ Standard library** **(STL)**][C_ Standard library_ _STL] provides arrays as a type of container which includes rich set of operations. It is a type template (a class template) defined in header **<array>**.

为了克服语言内置数组的问题， [**C ++标准库** **(STL)**][C_ Standard library_ _STL]将数组作为一种包含丰富操作集的容器提供。 它是在标题**<array>中**定义的类型模板(类模板)。

To work with that array we must include array header class in our code.

要使用该数组，我们必须在代码中包含数组标头类。

\#include<array> // Including array container header file

\#include <array> //包含数组容器头文件

These offer a better alternative for C-type arrays. The advantages over C-type arrays are:

这些为C型阵列提供了更好的选择。 与C型数组相比，优点是：

*  C-style arrays don’t know its own size. But Array Containers know their own size. So when passing array to a function here we no need to pass it’s size unlike where we do in C-type arrays.
    
    C样式的数组不知道其自身大小。 但是数组容器知道自己的大小。 因此，在此处将数组传递给函数时，与在C型数组中执行的操作不同，我们无需传递其大小。
 *  C-style arrays worked and entirely accessed by pointers, where Array Containers are not.
    
    C样式的数组可以工作，并且完全可以通过指针访问，而Array Container则不能。
 *  Array Containers have more inbuilt functions than C-style arrays. So these are more efficient.
    
    数组容器比C样式数组具有更多的内置函数。 因此这些效率更高。

### STL数组的语法 **(**Syntax of STL Array**)** ###

***array< datatype, size > arrayName;***

***array <数据类型，大小> arrayName;***

### 阵列容器上的操作 **(**Operations on Array Container**)** ###

Lets discuss about some important functions of stl array with program examples.

让我们用程序示例讨论stl数组的一些重要功能。

**at(): **This method used to access the elements of the array.

**at()：**此方法用于访问数组的元素。

**Syntax:** arrayName.at(index);

**语法：** arrayName.at(index);

In the place of index, if we give number more than the size of the array it will give array out\_out\_range exception.

在索引位置，如果我们给数字大于数组的大小，它将给数组out\_out\_range异常。

**get()**: This is also used to access the elements of the array. But this method doesn’t belongs to the class array. It is over loaded from class tuple.

**get()** ：这也用于访问数组的元素。 但是此方法不属于类数组。 它是从类元组重载的。

**Syntax:** get<index> (arrayName);

**语法：** get <索引>(arrayName);

**\[\] operator: **This is also used to access the elements of the array. This style accessing is same as C-style arrays.

**\[\]运算符：**这也用于访问数组的元素。 此样式访问与C样式数组相同。

**Example program to show about these three operations on array:**

**示例程序显示关于数组的这三个操作：**

#include <iostream>
    #include <array>
    #include <tuple> // This is for get() method
     
    using namespace std;
     
    int main(){
    	// Initializing arrays
    	array<int,5> marks = { 87, 98, 70, 90, 100};
    	
    	// accessing and printing array elements using at()
    	cout << "elements using at()" << endl;
    	for(int i=0;i<5;i++) cout << marks.at(i) << endl;
    	
    	// accessing and printing array elements using []  operator
    	cout << "elements using [] operator" << endl;
    	for(int i=0;i<5;i++) cout << marks[i] << endl;
    	
    	// accessing and printing array elements using get()
    	cout << "elements using get()" << endl;
    	cout << get<0> (marks)<<endl;
    	cout << get<1> (marks)<<endl;
    	cout << get<2> (marks)<<endl;
    	cout << get<3> (marks)<<endl;
    	cout << get<4> (marks)<<endl;
    	return 0;
    }

**Output**

**输出量**

*elements using at()* *87* *98* *70* *90* *100* *elements using \[\] operator* *87* *98* *70* *90* *100* *elements using get()* *87* *98* *70* *90* *100*

*使用at()的元素* *87* *98* *70* *90* *100* *使用\[\]运算符的元素* *87* *98* *70* *90* *100* *使用get()的元素* *87* *98* *70* *90* *100*

**front()**: This returns the first element of the array.

**front()** ：这将返回数组的第一个元素。

**back(): **This returns the last element of the array.

**back()：**这将返回数组的最后一个元素。

**Example program to show front() and back() operations:**

**显示front()和back()操作的示例程序：**

#include <iostream>
    #include <array>
     
    using namespace std;
     
    int main(){
    	array<int,5> marks = {87, 98, 70, 90, 100};
    	
    	// first element
    	cout << "first element of the array is ";
    	cout << marks.front() << endl;
    	
    	// last element
    	cout << "last element of the array is ";
    	cout << marks.back() << endl;
    	return 0;
    }

**Output**

**输出量**

*first element of the array is 87* *last element of the array is 100*

*数组的第一个元素是87数组的* *最后一个元素是100*

**size()**: It returns the number of elements in the array. C-style arrays fails in this.

**size()** ：返回数组中元素的数量。 C样式数组在此失败。

**max\_size(): **It returns the maximum number of elements array can hold i.e. the size with which array is declared. The size() and max\_size() return the same value.

**max\_size()：**返回数组可以容纳的最大元素数，即声明数组的大小。 size()和max\_size()返回相同的值。

**empty(): **If array size is zero this function returns true (1). Else returns false value

**empty()：**如果数组大小为零，则此函数返回true(1)。 否则返回假值

**fill()**: This function used to fill the entire array with particular value.

**fill()** ：此函数用于用特定值填充整个数组。

**Example program to demonstrate above four functions:**

**示例程序演示上述四个功能：**

#include <iostream>
    #include <array>
     
    using namespace std;
     
    int main(){
    	array<int,5> marks = { 87, 98, 70, 90 };
    	array<int,0> dup_array;
    	
    	// number of the elements in the array
    	cout << "the number of elements in the array is ";
    	cout << marks.size() << endl;
    	
    	// maximum number of elements array can hold
    	cout << "maximum number of elements in the array is ";
    	cout << marks.max_size() << endl;
    	
    	//checking size of array is empty or not
    	int flag = dup_array.empty();
    	if(flag==1) cout << "Array is empty" << endl;
    	else cout << "Array is not empty" << endl;
    		
    	// filling array with some particular element
    	marks.fill(35);
    	
    	//checking array after filling
    	for(int i=0;i<5;i++) cout << marks[i] << " ";
    	cout << endl;
    	return 0;
    }

**Output**

**输出量**

*the number of elements in the array is 5* *maximum number of elements in the array is 5* *Array is empty* *35 35 35 35 35*

*数组* *中元素的数量为5* *数组* *中元素的最大数量为5* *数组为空* *35 35 35 35 35*

**swap():** This will swap the all the elements of one array1 to array2 and from array2 elements to array1. But condition is that both arrays must be of same type and must be same size.  Swapping will done in such a way that, each ith indices of of both arrays will be swapped.

**swap()：**这会将一个array1的所有元素交换到array2，并从array2元素交换到array1。 但是条件是两个数组必须具有相同的类型并且必须具有相同的大小。 交换将以交换两个数组的第ith个索引的方式进行。

**Example program:**

**示例程序：**

#include <iostream>
    #include <array>
     
    using namespace std;
     
    int main(){
    	array<int,5> array1 = { 1, 2, 3, 4, 5 };
    	array<int,5> array2 = {11, 22, 33, 44, 55 };
    	
    	cout<< "array1 elements before swap" << endl;
    	for(int i=0;i<5;i++) cout << array1[i] << " ";
    	cout << endl;
    	
    	cout<< "array2 elements before swap" << endl;
    	for(int i=0;i<5;i++) cout << array2[i] << " ";
    	cout << endl;
    	
    	//doing swapping operation
    	array1.swap(array2);
    	
    	cout<< "array1 elements after swap" << endl;
    	for(int i=0;i<5;i++) cout << array1[i] << " ";
    	cout << endl;
    	
    	cout<< "array2 elements after swap" << endl;
    	for(int i=0;i<5;i++) cout << array2[i] << " ";
    	cout << endl;
    	return 0;
    }

**Output**

**输出量**

*array1 elements before swap* *1 2 3 4 5*  *array2 elements before swap* *11 22 33 44 55*  *array1 elements after swap* *11 22 33 44 55*  *array2 elements after swap* *1 2 3 4 5*

*交换之前ARRAY1元素* *之前* *1 2 3 4 5个* *数组2元件* *交换后* *11 22 33 44 55个* *元素数组2* *交换之后* *交换* *11 22 33 44 55* *ARRAY1元件* *1 2 3 4 5*

Comment below if you have any queries or found any information incorrect in above tutorial for C++ STL Array.

如果您对上面的C ++ STL Array教程有任何疑问或发现任何不正确的信息，请在下面评论。

> 翻译自: [https://www.thecrazyprogrammer.com/2017/07/stl-array.html][https_www.thecrazyprogrammer.com_2017_07_stl-array.html]

c++stl和std

[7cb3a601c4bf448d05a623805a35b8d8.png]: /images/20221123/3df58373d6704d0c97cafa97e766bd4a.png
[C_ Standard library_ _STL]: https://www.thecrazyprogrammer.com/2017/07/c-standard-template-library-stl.html
[https_www.thecrazyprogrammer.com_2017_07_stl-array.html]: https://www.thecrazyprogrammer.com/2017/07/stl-array.html