代码

#include<stdio.h>
int max1(int num1,int num2)
{
    if(num1 < num2)
    {
        num1 = num2;
    }
    else
    {
        num2 = num1;
    }
}
int max2(int *num1,int *num2)
{
    if(num1 < num2)
    {
        *num1 = *num2; // 把 num2 赋值给 num1 
    }
    else
    {
        *num2 = *num1;
    }
}
int main()
{
    int num1 = 0,num2 = -2;
    int ret;
    max1(num1,num2);

    printf("num1 is %d\n",num1);
    printf("num2 is %d\n",num2);

    max2(&num1,&num2); //&num1 表示指向 num1 的指针，即变量 num1 的地址

    printf("num1 is %d\n",num1);  
    printf("num2 is %d\n",num2);

    return 0;
}

结果