帮忙用C/C++程序编写一个简单程序

我用c++编一个：
#include<iostream.h>
void main() {
int a,b,c,max;
cout<<"请输入3个整数:"<<'\n';
cin>>a>>b>>c;
max=((a>b)?((a>c)?a:c):((b>c)?b:c));
cout<<"max="<<max;
}

#include<stdio.h>
void main()
{
int a,b,c;
printf("输入3个整数:");
scanf("%d %d %d",&a,&b,&c);
if(a>b)
b=a;
if(b<c)
b=c;
printf("%d",b);
}

#include <iostream.h>
#include <string>
int max(int a=0,int b=0,int c=0)
{ int max;
if(a>b)
max=a;
else
max=b;
if(a>c)
max=a;
else
max=c;
return max;
}
void main()
{
int a,b,c;
cout<<"input three numbers:";
cin>>a;
cin>>b;
cin>>c;
cout<<"max is:"<<max(a,b,c)<<