练习：文件读写，类的继承与重载

文件流读写：

#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;
int main()
{
	fstream in,out;
	int a[10],i,n=0;
	in.open("1.txt",ios::in);
	while(!in.eof())
		in>>a[n++];
	in.close();
	sort(a,a+n);
	out.open("ans.txt",ios::out);
	for (i=0;i<n;i++)
		out<<a[i]<<" ";
	out.close();
	return 0;
}

结构体读写：

#include<iostream>
#include<fstream>
#include<algorithm>
#include<string>
using namespace std;
struct P
{
	string name;int val;
	P(){name="";val=0;}
	P(string s,int x){name=s;val=x;}
};
int main()
{
	fstream in,out;
	P A("zjw",8),B;
	out.open("person.txt",ios::out);
	out.write((char*)&A,sizeof(A));
	out.close();
	in.open("person.txt",ios::in);
	in.read((char*)&B,sizeof(B));
	cout<<B.name<<" "<<B.val<<endl;
	return 0;
}

c++类的继承与函数重载：

#include<iostream>
#include<string>
using namespace std;
class Rec
{
public:
	int w,d;
	Rec(){};
	Rec(int a,int b){ w=a;d=b;}
	Rec(Rec &A) { w=A.w;d=A.d;}
	bool operator == (const Rec &A)
	{	return (w==A.w && d==A.d); }
};
class RRec: public Rec
{
public:
	int s;
	RRec(int a,int b):Rec(a,b){}
	void square(){ s=w*d; }
	bool operator < (const RRec &A)const
	{	return s<A.s; }
};
int main()
{
	RRec a(3,4),c(2,5);
	RRec b(a);
	a.square();c.square();
	cout<<(a==b)<<endl;
	cout<<(c<a)<<endl;
}