指针数组 c ++

介绍 (Introduction)

Today in this tutorial, we are going to understand the concept of the Pointer to Array in C++.

今天，在本教程中，我们将了解C ++中的数组指针的概念。

Before we head directly to the topic, we first would like to guide the readers through the pointer arithmetics in C++. It is going to help understand the concept in a better way.

在直接进入该主题之前，我们首先要引导读者学习C ++中的指针算法。 这将有助于更好地理解该概念。

指针算术 (Pointer Arithmetics)

Basically, pointers are variables that store the address of any other variable of a specific data type.

基本上， 指针是存储特定数据类型的任何其他变量的地址的变量。

Let us go through a simple example to get a clear idea about the pointer arithmetics.

让我们来看一个简单的示例，以清楚地了解指针算法。

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{  int  i = 3, *x; float  j = 1.5, *y; cout<<"Value of i= "<<i;cout<<"\nValue of j= "<<j;  x = &i ;y = &j ;//Original pointer valuesprintf("\nOriginal address in x = %u",x);printf("\nOriginal address in y = %u",y);//Increasing pointer addressesx++ ;y++ ;//After incrementprintf("\nNew address in x = %u",x);printf("\nNew address in y = %u",y);cout<<"\n\nSize of int for this compiler = "<<sizeof(int);cout<<"\nSize of float for this compiler = "<<sizeof(float);return 0;
}

Output:

输出：

Value of i= 3
Value of j= 1.5
Original address in x = 7339516
Original address in y = 7339512
New address in x = 7339520
New address in y = 7339516Size of int for this compiler = 4
Size of float for this compiler = 4

Here,

这里，

• We first initialize two int and float variables i and j respectively with some values,我们首先用两个值分别初始化两个int和float变量i和j，
• Then we store the address of the two variables inside two pointers x and y in lines 11 & 12, and print them out,然后，将这两个变量的地址存储在第11和12行的两个指针x和y中，并将它们打印出来，
• After that, we increment both the pointers and see the change in output.之后，我们将两个指针都递增，并看到输出的变化。

Observe the 5th and 6th lines of the output. 7339520 is original value in x plus 4, and 7339516 is original value in y plus 4. This so happens because every time a pointer is incremented it points to the immediately next location of its type.

观察输出的第5行和第6行。 7339520是x加上4的原始值，而7339516是y加上4的原始值。这是因为每次指针递增时，它都指向该类型的下一个位置。

That is why, when the integer pointer x is incremented, it points to an address two locations after the current location since an integer is always 4 bytes long (We checked that using the sizeof() function above).

这就是为什么当整数指针x递增时，它指向当前位置后两个位置的地址，因为整数始终长4个字节（我们使用上面的sizeof（）函数进行了检查）。

Similarly, y points to an address 4 locations after the current location. This is a very important result and can be effectively used while passing the entire array to a function.

同样， y指向当前位置之后4个位置的地址。 这是非常重要的结果，可以在将整个数组传递给函数时有效地使用。

Note: Do not attempt the following operations on pointers, they would never work,

注意：请勿尝试对指针执行以下操作，否则它们将永远无法工作，

• Addition of two pointers,两个指针相加，
• Multiplication of a pointer with a constant,指针与常数相乘，
• Division of a pointer with a constant.用常数除以指针。

C ++中的指针和数组 (Pointers And Arrays in C++)

Now, let us take a deep look at accessing array elements using pointers.

现在，让我们深入了解如何使用指针访问数组元素。

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{  int arr[4]= { 10, 20, 30, 40 };int *ptr;ptr=&arr[0]; //same as ptr=arr(arr is the base address)//printing address and values of array//elements using pointersfor(int i=0; i<4; i++){printf("\nAddress = %u",(ptr+i));cout<<"\tValue = "<<*(ptr+i);}return 0;
}

Output:

输出：

Address = 7339504       Value = 10
Address = 7339508       Value = 20
Address = 7339512       Value = 30
Address = 7339516       Value = 40

In the code above,

在上面的代码中，

• At first, we initialize an array of size 4 and a pointer for the same type,首先，我们初始化一个大小为4的数组和一个相同类型的指针，
• After that, we assign the base address or the address of the 1st element of the array to the pointer(Since, arr and &arr[0] are same), ptr,之后，我们将基地址或数组第1个元素的地址分配给指针（因为arr和&arr[0]相同） ptr ，
• Then we print out the elements and their corresponding addresses using pointers.然后，我们使用指针打印出元素及其对应的地址。

As we discussed in the previous section, (ptr+i) is the address of the ith element from the array arr. And *(ptr+i) actually refers to the value at the address (ptr+i). Therefore, it gives us the value of the ith element.

如上一节所述， (ptr+i)是数组arr中第ith个元素的地址。 *(ptr+i)实际上是指地址（ptr + i）上的值 。 因此，它为我们提供了第ith个元素的值。

使用指针将数组传递给函数 (Passing An Array to Function Using Pointers)

Let us see how we can pass a whole array to a function with the help of pointers as an example, to get a clear understanding of the topic.

让我们看看如何在指针的帮助下将整个数组传递给函数，以使您对该主题有一个清晰的了解。

#include<iostream>
using namespace std;
void show(int *ptr, int n)
{//printing the whole arrayfor(int i=0; i<n; i++){cout<<"arr["<<i<<"] = "<<*(ptr+i)<<endl;}
}
int main()
{  //Array initialisationint arr[5]= { 12, 45, 86, 73, 87 };show( arr, 5);//function call with base address(arr) and no.of elements(6)return 0;
}

Output:

输出：

arr[0] = 12
arr[1] = 45
arr[2] = 86
arr[3] = 73
arr[4] = 87

Similar to the previous example, here we initialize an array inside the main() and pass the base address arr and the array size as parameters to the show() function we defined before.

与前面的示例类似，这里我们在main()内部初始化一个数组，并将基地址arr和数组大小作为参数传递给我们之前定义的show()函数。

After the call of the show() function, at this point, the pointer ptr stores the base address of the array(arr) and n is the size. Further, we use a for loop to print the whole array using the concept of a pointer to array.

在调用show（）函数之后，此时，指针ptr存储array（arr）的基地址， n为大小。 此外，我们使用for循环使用指向数组的指针的概念来打印整个数组。

结论 (Conclusion)

So, in this tutorial, we learned the working as well as the use of the Pointers to Arrays in C++. Practicing the above codes/examples would help understand the topic further.

因此，在本教程中，我们学习了C ++中指向数组的指针的工作方式和用法。 练习以上代码/示例将有助于进一步理解该主题。

For any questions, feel free to use the comments below.

如有任何疑问，请随时使用以下评论。

参考资料 (References)

• Pointers to 2D Arrays in C++ – Journal Dev post,指向C ++中2D数组的指针 – Journal Dev post，
• Pointers in C & C++ – Journal Dev Post,C＆C ++中的指针 – Journal Dev Post，
• Is an array name a pointer? – Stack Overflow Question.数组名称是指针吗？ –堆栈溢出问题。

翻译自: https://www.journaldev.com/37702/pointer-to-array-in-c

指针数组 c ++