通過使用指針指針來更改引用

Question

在下面的代碼中，期望的輸出是1.但它變成了2.引用如何改變？

#include <stdio.h> 

int main() 
{ 
    int a = 1, b = 2, c = 3; 
    int *ptr1 = &a, *ptr2 = &b, *ptr3 = &c; 
    int **sptr = &ptr1; //-Ref 
    *sptr = ptr2; 
    printf("%d",*ptr1); 
} 

Answer 1

int main() 
{ 
    int a = 1, b = 2, c = 3; 
    int *ptr1 = &a, *ptr2 = &b, *ptr3 = &c; 

    // ptr1 points to a 
    // ptr2 points to b 



    int **sptr = &ptr1; //-Ref 
    // *sptr points to ptr1 , that means **sptr points indirectly to a 

    *sptr = ptr2; //this translates in ptr1 = ptr2, that means ptr1 points to what ptr2 pointed 
    return 0; 
} 

Answer 2

int a = 1, b = 2, c = 3; 
int *ptr1 = &a, *ptr2 = &b, *ptr3 = &c; 

ptr1的值是a的地址，ptr2值爲b的地址。

int **sptr = &ptr1; // sptr has address of ptr1 

由於sptr指向ptr1（它的值是ptr1的地址），通過使用*sptr我們可以改變的ptr1值。

*sptr = ptr2; //here we are altering contents of sptr and value of ptr1. 

所以現在ptr1點，其中ptr2一樣。致b = 2;