指针逻辑

Question

我一般都知道了指针的逻辑,但对于我来说,有一点与下面的代码有关.

#include <iostream>
using namespace std;

int main ()
{
int first = 50, 
second = 150;
int * p1, * p2;

p1 = &first;         //p1 is assigned to the address of first
p2 = &second;        //p2 is assigned to the address of second
*p1 = 100;           //first's value is changed as 100 by assigning p1's value to 100
*p2 = *p1;           //now p2's value should be 100 
p1 = p2;             //I think we want to change p1's adress as p2
*p1 = 200;           //I expect that the new value of p1 should be 200

cout << first << second;

return 0;
}

程序打印首先= 100和秒= 200,但正如我在上面评论的那样,我预计p1的值会改为200.但它仍然保持为100.重点是什么？

Answer 1

您似乎将指针值与指针指向的值混淆.

*p1 = 200;           //I expect that the new value of p1 should be 200

p1是一个指针,所以它的值实际上是一个内存位置,位置first.(像0xDEADBEAF).在此之后:

p1 = p2;

p1是指向内存位置second,所以在做的时候

*p1 = 200;

它实际设置second为200.