二级指针与指针数组

#include <stdio.h>  
#include <stdlib.h>  
  
int main() {  
    // 定义一个指针数组，每个元素都是一个指向int的指针  
    int *ptr_array[3];  
  
    // 为指针数组的每个元素分配内存  
    ptr_array[0] = malloc(2*sizeof(int));  
    ptr_array[1] = malloc(2*sizeof(int));  
    ptr_array[2] = malloc(2*sizeof(int));  
  
    printf("%d\n", sizeof(int));  
    printf("%d\n", sizeof(int*));  
    printf("%d\n", sizeof(ptr_array));  

 
    // 定义一个二重指针，让它指向指针数组的第一个元素  
    int **double_ptr = &ptr_array[0];  
    //赋值方式
	(double_ptr[0][0]) = 40; 
	(double_ptr[1][0]) = 50; 
	(double_ptr[2][0]) = 60; 
	(double_ptr[0][1]) = 70; 
	(double_ptr[1][1]) = 80; 
	(double_ptr[2][1]) = 90; 
	
	
    // 通过二重指针访问和打印指针数组的元素  
    for (int i = 0; i < 3; i++) {
           //指针数组中每个元素占用8字节，代表指针数组元素的地址
        printf("double_ptr[%d] points to a value of %d\n", i, &(double_ptr[0])+i);  
        printf("double_ptr[%d] points to a value of %d\n", i, (double_ptr+i));  
	   	printf("double_ptr[%d] points to a value of %d\n", i, (&double_ptr[i]));  

        //代表每行第2元素中的地址
        printf("double_ptr[%d] points to a value of %d\n", i, *(&(double_ptr[0])+i)+1);
		printf("double_ptr[%d] points to a value of %d\n", i, *(double_ptr+i)+1); 
	    printf("double_ptr[%d] points to a value of %d\n", i, (double_ptr[i]+1));  
	   	printf("double_ptr[%d] points to a value of %d\n", i, &(double_ptr[i][0])+1); 
		printf("double_ptr[%d] points to a value of %d\n", i, &(double_ptr[i][1])); 

        //代表每行第二个元素值所指空间的内容
		printf("double_ptr[%d] points to a value of %d\n", i, *(*(&(double_ptr[0])+i)+1));
		printf("double_ptr[%d] points to a value of %d\n", i, *(*(double_ptr+i)+1));
	    printf("double_ptr[%d] points to a value of %d\n", i, *(double_ptr[i]+1));
		printf("double_ptr[%d] points to a value of %d\n", i, *(&(double_ptr[i][0])+1)); 
		printf("double_ptr[%d] points to a value of %d\n", i, (double_ptr[i][1])); 

        
    }  
  
    // 释放内存  
    for (int i = 0; i < 3; i++) {  
        free(ptr_array[i]);  
    }  
  
    return 0;  
}

二维数组、及通过二级指针访问二维数组

#include <stdio.h>  
#include <stdlib.h>  
  
int main() {  
    int a[3][2] = {
                    {1,2},
                    {3,4},
                    {5,6}
                  };
    //&a整个数组的地址，a数组首行地址，*a数组首行第一个元素地址，**a数组第一个元素的值
    printf("%d,%d,%d,%d\n",&a, a,*a,**a);
    
    //解释方式与上条语句类似
    printf("%d,%d,%d,%d\n",&a, &a[0],&a[0][0],a[0][0]);
    
    //第一种：二维数组指针，指向整个二维数组
    int (*ptr)[3][2]=&a;
    
    //第二种：一维数组指针，指向二维数组第一行元素
    int (*ptr1)[2]=a;//or &a[0]
    
    //第三种：int *型指针，指向二维数组第一行第一列的第一个元素
    int *ptr2=&a[0][0];//or *a
    
    //第四种：二级指针与二维数组结合
    int **ptr3 = calloc(3, sizeof(int *));
    for (int i = 0; i < 3; ++i) {
       	*(ptr3+i)=*(a+i);
       	printf("%d,%d\n",*(*(ptr3+i)+0),*(*(ptr3+i)+1));
    }
    
    int **ptr4 = calloc(3, sizeof(int *));
    for (int i = 0; i < 3; ++i) {
        printf("%d,%d\n",a+i,*(a+i));
       	*(ptr4+i)=(a+i);
       	printf("%d,%d\n",*(*(ptr4+i)+0),*(*(ptr4+i)+1));
    }
    return 0;  
}

二维数组指针

#include <stdio.h>  
#include <stdlib.h>  
  
int main(int argc, char **argv) {
    //二维数组指针
    int (*ptr)[3][3] = calloc(3 * 3, sizeof(int));
    //&ptr:二维数组指针的地址
    //ptr:二维数组的首地址，代表整个数组
    //*ptr:二维数组的首行首地址，代表整行
    //**ptr:二维数组的首个元素的地址，代表数组的第一个元素
    printf("%d,%d,%d,%d\n",&ptr,ptr,*ptr,**ptr);
    //赋值
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            (*ptr)[i][j]=j;
            
        }
    }
    
    for (int i = 0; i < 3; ++i) {
        printf("%d,%d,%d\n",(*ptr)[i],(*ptr)+i,*((*ptr)+i));
    }
    
    for (int i = 0; i < 3; ++i) {
        printf("%d,%d\n",*((*ptr)[i]),**((*ptr)+i));
    }
    
    //打印
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            printf("%d", (*ptr)[i][j]);
        }
        printf("\n");
    }
    return 0;
}