如果要通过函数改变一个指针的值，要往函数中传入指针的指针
如果要通过函数改变一个变量的值，那就要往函数中传入这个变量的地址

改变a的值和b的值

#include <iostream>

using namespace std;

void swap(int* a, int* b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

int main() {
    int a = 10;
    int b = 20;
    int* pa = &a;
    int* pb = &b;

    cout << a << endl; // 10
    cout << b << endl; // 20
	
	//需要传入a和b的地址
    swap(pa,pb);
    cout << "-------swap()--------" << endl;
    cout << a << endl; // 10
    cout << b << endl; // 20

    return 0;
}

改变pa的值和pb的值

#include <iostream>

using namespace std;

void changepoint(int** ppa, int** ppb) {
    int* temp = *ppa;   //*ppa=1000=*1090=*(&pa)=pa
    *ppa = *ppb;
    *ppb = temp;
}

int main() {
    int a = 10;
    int b = 20;
    int* pa = &a;
    int* pb = &b;
    cout << *pa << endl; // 10
    cout << *pb << endl; // 20

    //需要传入pa和pb的地址
    changepoint(&pa, &pb);
    cout << "-------changepoint()--------" << endl;
    cout << *pa << endl; // 10
    cout << *pb << endl; // 20

    return 0;
}