油院c++答案

字符串拼接
#include <iostream>
using namespace std;
#define L 40
void main()
{char s1[L+ 1],s2[L + 1];char r[2 * L + 1];int i=0,j=0;cout<<"Input the first string:"<<endl;cin.get(s1,8);cout<<"Input the second string."<<endl;cin.get(s2,8);
while(s1[i] != '\0') { r[i] = s1[i]; i ++;}
while(s2[j] != '\0') { r[i] = s2[j]; i++; j++;} r[i] = '\0'; cout<<r<<endl;
}

圆周长
#include <iostream.h>
class qiu
{
public:
qiu(double r=0):banjing(r){}
double mianji()
{ return 3.14 * banjing *banjing; }
friend double zhouchang(const qiu &c);
private:
double banjing;
};
double zhouchang(const qiu &c)
{
return 2.* 3.14 * c.banjing;
}

int main()
{
qiu a(10);
cout<<"面积: "<<a.mianji()<<endl;
cout<<"周