14- arrays and pointers

& Addressing operator

* Pointer operator

& Addressing operator and * pointer operator

It has the same priority, from right to left binding.

int a;

Int *p=&a;

*&a---->a

&*p---->p

int *p=&a;

Pointer assignment:

When it was declared: assignment int * p = & a;

First statement by assignment: int A; int * the p-; the p-& = A;

* p occur when the individual is the data.

int * p preceded by a data type.

A one-dimensional arrays and pointers.

1, one-dimensional array address.

It is the address of the first element of the array.

1 #include <stdio.h>
2 
3 int main()
4 {
5 int arr[5];
6 printf("%d\n", &arr[0]);
7 
8 return 0;
9 }

Definition of a pointer, the first address of the one-dimensional array of & a [0] gives the pointer ptr , said ptr pointer to the array A [. 5] .

An array array name is the first address of the array. arr [5] & arr [0 ] == arr == ptr

2, one-dimensional array for input and output.

A, the pointer is not changed.

 1 #include <stdio.h>
 2 
 3 int main()
 4 {
 5     //int arr[5];
 6 
 7     //for (int i = 0; i < 5; i++)
 8     //{
 9         // arr[i] = i + 1;
10     //}
11 
12 
13     //for (int i = 0; i < 5; i++)
14     //{
15         // printf("arr[%d]=%d\n", i, arr[i]);
16     //}
17 
18 
19     int arr[5];
20     intARR = p *;    // int * p = & ARR [0]; 
21 is  
22 is      for ( int I = 0 ; I < . 5 ; I ++) // I 0-4 
23 is      {
 24          // after long pointer variable p is declared finished address * p is to accompany the address of the variable pointed. 
25          * (P + I) = I + . 1 ; // ARR [0] - P * ARR [. 1] - * (P +. 1) ARR [2] - * (P + 2) 
26 is      }
 27  
28       
29      for ( int I = 0 ; I < . 5 ; I ++ )
 30      {
 31 is          the printf ( "arr[%d]=%d\n", i, *(p + i));
32     }
33 }

* Only when expressed in a statement that is a pointer to any other situation alone * have said pointer operator.

B, the array index is a pointer p is changed, it must be put before printing p redirected to the array of the first address.

 1 int arr[5];
 2 int *p = arr;   // int *p=&arr[0];
 3 
 4  
 5 /********************************
 6 1: *p         -- arr[0]    1
 7 2: *(p+1)     -- arr[1]    2
 8 3: *((p+1)+1) -- arr[2]    3
 9 ********************************/
10 
11 printf("赋值之前：%d\n", p);
12 
13 for (int i = 0; i < 5; i++) //i 0-4
14 {
 15      * p ++ = I + . 1 ; // Can 1-5 p is copied to the array changes  
 16      // value of an expression which is the first calculation expression p ++ in +. 1 to p
 . 17      @ ++ p p + 1 then give calcd expression 
18 is  }
 . 19  
20 is the printf ( " after this assignment:% D \ n- " , P);
 21 is  
22 is  for ( int I = 0 ; I < . 5 ; I ++ )
 23 is  {
 24      the printf ( " ARR [D%] D =% \ n- " , I, ARR [I]);
 25  }
 26 is  
27   
28 P = & ARR [0 ]; // first address of the p redirected array 
29 the printf ( " before printing:% D \ n- " , p);
 30  
31 is   
32  for ( int I = 0 ; I < . 5 ; I ++ )
 33 is  {
 34 is      the printf ( " ARR [D%] D =% \ n- " , I, P * ++ );
 35  }
 36  
37 [ the printf ( " after printing:% D \ n- " , P);

Recommendation: meet pointers: 1 , the pointer to type? 2 , where the pointer points? 3 pointer own type?

Second, the two-dimensional arrays and pointers.

1, address two-dimensional array.

First Address:

&a[0][0] a[0] &a[0] a &a

行地址：

1、第0行的地址就是首地址

2、第1行 &a[1][0] a[1] &a[1] a+1

3、第2行 &a[2][0] a[2] &a[2] a+2

4、第i行 &a[i][0] a[i] &a[i] a+i

蓝色的加法就加一维数组的字节数橙色的加法加数据类型的字节数

通过行地址去找到n行m列的元素。

&a[n][m] a[n]+m (关键是要搞清楚以一维数组老做判断还是以整体的二维数组来进行判断 )

//n行m列的元素

*(a[n]+m)

*(*(a+n)+m) //a+n a[n] *(a+n) a[n]+m

下节课：

字符串和指针（数组和指针）指针类型的数组

函数和指针

指针总结

结构体

预处理

位运算

数据结构

写项目

14- arrays and pointers

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