[C] 三種函數方法的調用， 引用調用與指針

三種函數方法的調用，

主要看change3這個函數, 此方法調用後， 會對主函數造成影響！

#include <stdio.h>

void change1(int a, int b)
{
    if(a<b)
    {
        int temp;
        temp = a;
        a = b;
        b = temp;
    }
    printf("change1: a = %d, b = %d \n",a,b);
}

void change2(int *p1, int *p2)
{
    if(*p1<*p2)
    {
        int *temp;
        temp = p1;
        p1 = p2;
        p2 = temp;
    }
    printf("change2: a = %d, b = %d \n",*p1,*p2);
}

void change3(int *p1, int *p2)
{
    if(*p1<*p2)
    {
        int temp;
        temp = *p1;
        *p1 = *p2;
        *p2 = temp;
    }
    printf("change3: a = %d, b = %d \n",*p1, *p2);
}

int main()
{
    int a, b;
    int *p1,*p2;
    printf("Input two number:\nfirst:");
    scanf("%d",&a);
    printf("second:");
    scanf("%d",&b);
    p1 = &a;
    p2 = &b;

    change1(a,b);    /*方法change1中調換兩個數的位置，不會對主函數有影響*/
    printf("main: a = %d, b = %d \n",a,b);

    change2(p1,p2);  /*方法change2中調換兩個婁的位置，不會對主函數有影響*/
    printf("main: a = %d, b = %d \n",a,b);

    change3(p1,p2);  /*方法change3中調換兩個數的位置，會對函數主有影響*/
    printf("main: a = %d, b = %d \n",a,b);
}