Array of pointers (i)

The definition and use of pointers to different types of variables are described earlier. We can let the pointer point to a class of variables, and replace the variable in the program, we can also let the pointer point to a one-dimensional, two-dimensional array or character array, to replace these arrays in the program to use, give us a lot of convenience in programming.

Here we define a special array, which holds all pointers, which are used to point to variables of a class, in place of the variables used in the program, to increase flexibility. Pointer array definition form:

Type ID * array name [array length]

For example: Char *str[4];

Because [] is higher than the * priority, so the first is the array form Str[4], and then the "*" binding. Thus the pointer array contains 4 pointers s t r [0], S t r [1], S t R [2], S t R [3], each pointing to a variable of the character type. For example:

int *p T R [5];

The pointer array contains 5 pointers p T r [0], p t R [1], P t R [2], P t R [3], p t R [4], and each point to a variable of an integer type.

[Example 6-22] for the application of pointer arrays, we respectively point to the array of strings, point to one-dimensional integer array, and point to a two-dimensional integer array with each pointer in the array of pointers.

#include <stdlib.h>
#include <stdio.h>
m a i n ( )
{
char *ptr1[4]={"china","chengdu","sichuang","chongqin"};
/* 指针数组p t r 1 的4个指针分别依此指向4个字符串* /
int i,*ptr2[3],a[3]={1,2,3},b[3][2]={1,2,3,4,5,6};
for(i=0;i<4;i++)
printf("\n%s",ptr1[i]);/依*此输出ptr1数组4个指针指向的4个字符串*/
printf("\n");
for(i=0;i<3;i++)
ptr2[i]=&a[i];/*将整型一维数组a的3个元素的地址传递给指针数组ptr2*/
for(i=0;i<3;i++)/*依此输出ptr2所指向的3个整型变量的值*/
printf("%4d",*ptr2[i]);
printf("\n");
for(i=0;i<3;i++)
ptr2[i]=b[i];/*传递二维数组b的每行首地址给指针数组的4个指针*/
for(i=0;i<3;i++)/*按行输出*/
printf("%4d%4d\n",*ptr2[i],*ptr2[i]+1);
}

The relationship between the pointer array and the object in the program is shown in Figure 6-12.

The 4 pointers in the PTR1 pointer array point to 4 strings, respectively. As shown in Figure 6-11 (a), this output is in the program; there are 3 pointers to the PTR2 pointer array, and if you pass each element address in the integer one-dimensional array A to each pointer in the pointer array, ptr2[0] points to a[0];ptr2[1 Point to a[1];ptr2[2] and point to a[2]. If you pass the first address of each row in a two-dimensional array to each pointer in an array of pointers, as shown in Figure 6-11b), Ptr2[0] points to line No. 0 of the B array, which has two elements, with the address ptr2[0] and ptr2[0]+1, and the first element of the corresponding pointer array ptr2[i] The two element addresses in line I of point B array are ptr2[i] and ptr[i]+1.