Related problems of pointer array, array pointer and parameter passing

Catalog

Catalog

1. Pointer array ： An array of pointers , It's an array , It's just that it doesn't store integers 、 Floating point but pointer .

2. Array pointer ： A pointer to an array , It's a pointer .

3. The ginseng

  Conclusion ：

---

Pointer array ： An array of pointers , It's an array , It's just that it doesn't store integers 、 Floating point but pointer

form ：int* arr[10] :

Be careful ：arr Is and [ ] First combine with * combination , because [ ] The priority ratio * high

Use ：

Through the pointer array , We can use one-dimensional array to realize two-dimensional array  

#include <stdio.h>

int main()
{
	int arr1[] = { 1,2,3,4,5 };
	int arr2[] = { 2,2,3,4,5 };
	int arr3[] = { 3,2,3,4,5 };

	int* parr[3] = { arr1,arr2,arr3 };

	int i = 0;
	for (i = 0; i < 3; i++)
	{
		int j = 0;
		for(j=0;j<5;j++)
		{
			printf("%d ", *(parr[i] + j));
		}
		printf("\n");
	}

	return 0;
}

---

Array pointer ： A pointer to an array , It's a pointer .

We all know ：

Integer pointer ： A pointer that can point to shaped data

Floating point pointer ： A pointer that can point to floating-point data

Array pointer ： A pointer to an array , It's a pointer .

form ： int (*p2) [10];  It's a Array pointer , It's an array , The array has 10 Elements , Every element int type ,p2 Is a pointer array minus p2, The rest is p2 The type of ,int(* ) [10]

notes ： because p1 Is and [ ] First combine with * combination , because [ ] The priority ratio * high

Use ：

Want to use array pointers well , First, master the following contents ： 

We know that the array name is usually the address of the first element of the array , But there are two exceptions ！！

special ： The following is the address of the entire array

* sizeof( Put a separate array name ), notes ：sizeof(arr+0) Do not put an array name alone

* & Array name ,

Look at the code ：（arr It represents the address of the first element of the array , Writing with a pointer array is complicated ）

The following cases are less useful , Array pointers are commonly used for 2D and 3D arrays

int main()
{
	int arr[] = { 1,2,3,4,5,6,7,8,9 };
	int(*p)[9] = &arr;

	int i = 0;
	for (i = 0; i < 9; i++)
	{
		printf("%d ", *(*p + i));
	}

	return 0;
}

 

（ When the argument is a two-dimensional array name , Formal parameters can be received with array pointers ）

  Particular attention ：

* This topic arr It's an array name , Represents the address of the first element of the array

* The first element of a two-dimensional array is the first row of the two-dimensional array （ Passed by this topic arr, Is the address of a one-dimensional array ）

* Receive a pointer , This pointer points to an array , So we can use array pointer to realize

  The above code is as follows ：

#include <stdio.h>

void print_arr1(int arr1[3][5], int row, int col)
{
	int i = 0;
	for (i = 0; i < row; i++)
	{
		int j = 0;
		for (j = 0; j < col; j++)
		{
			printf("%d ", arr1[i][j]);
		}
		printf("\n");
	}
}

void print_arr2(int(*p)[5], int row, int col)
{
	int i = 0;
	for (i = 0; i < row; i++)
	{
		int j = 0;
		for (j = 0; j < col; j++)
		{
			printf("%d ", *(*(p + i) + j));
		}
        printf("\n");
	}
}

int main()
{
	int arr[3][5] = { 1,2,3,4,5,6,7,8,9,10 };
	
	print_arr1(arr, 3, 5);

	print_arr2(arr, 3, 5);

	return 0;
}

---

The ginseng

The above involves array parameter passing , In this section, I will summarize the parameters of one-dimensional array 、 Two dimensional array parameters 、 First level pointer parameter transfer 、 The core content of two-level pointer parameter transfer

One dimensional array parameters

①

 

 ②

  The code is as follows ：

void test1(int arr[10])
{}
void test1(int arr[])
{}
void test1(int* p)
{}

int main()
{
	// One dimensional array 
	int arr[10] = { 0 };

	test1(arr);

	return 0;
}


void test2(int* arr2[20])
{}
void test2(int** p)
{}

int main()
{
	// Pointer array pass parameter 
	int* arr2[20] = { 0 };

	test2(arr2);

	return 0;
}

---

Two dimensional array parameters ：

Array name of two-dimensional array , Represents the address of the first element , It's actually the address on the first line

  The code is as follows ：

void test(int arr[3][5])
{}
void test(int arr[][5])
{}
void test(int arr[][])
{}

void test(int (*arr)[5])
{}
void test(int* arr)
{}
void test(int* arr[5])
{}
void test(int** arr)
{}
int main()
{
	int arr[3][5] = { 0 };

	test(arr);

	return 0;
}

---

  First level pointer parameter transfer ：

Take a different perspective , If the argument part of a function is a pointer , How to write the arguments

  The code is as follows ：

void print(int* p)
{}

int main()
{
	int a = 10;
	int* ptr = &a;
	int arr[10] = { 0 };

	print(&a);

	print(ptr);

	print(arr);

	return 0;
}

---

The secondary pointer transmits parameters ：

Another angle , If the formal parameter of a function is a second-order pointer , How to write the arguments

  The code is as follows ：

void test(int** p)
{}

int main()
{
	int* p1;
	int** p2;
	int* arr[10];

	test(&p1);

	test(p2);

	test(arr);

	return 0;
}

---

  Conclusion ：

If it helps you ,

Don't forget it give the thumbs-up + Focus on Oh , Crab

If it helps you ,

Don't forget it give the thumbs-up + Focus on Oh , Crab

If it helps you ,

Don't forget it give the thumbs-up + Focus on Oh , Crab