第七章作业

#include<iostream>
#include"math.h"
using namespace std;
void Rec()
{
int a, b, c;

float area , s ;

cout << "输入三角形三条边：" << endl;

cin >> a >> b >> c;

s = (a + b + c) / 2;

area = sqrt(s * (s-a) * (s-b) * (s-c));

if((a+b<=c) || (b+c<=a) || (c+a<=b))
{
cerr << "ERROR" << endl;
}

cout << "这个三角形的面积是：" << area << endl;

}

int main()
{
Rec();
return 0;
}

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
float a[5];

cout<<"input data:";

int i=0;

for( i=0;i<5;i++)
{
cin>>a[i];
}
cout << setiosflags(ios::fixed) << setprecision(2);

for(i=0;i<5;i++)
{
cout<<setw(10)<<a[i]<<endl;
}

return 0;
}

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
for(int n=1;n<8;n++)
{
cout << setw(20-n) << setfill(' ') << " "
<< setw(2*n-1) << setfill('B') << "B" << endl;
}

return 0;
}

#include <iostream>
#include <fstream>
using namespace std;
//fun1函数从键盘输入20个整数，分别存放在两个磁盘文件中

void fun1()
{
int a[10];

ofstream outfile1("f1.dat"),outfile2("f2.dat");  //分别定义两个文件流对象

if(!outfile1)                        //检查打开f1.dat是否成功

{
cerr<<"open f1.dat error!"<<endl;

exit(1);
}

if(!outfile2)                        //检查打开f2.dat是否成功
{
cerr<<"open f2.dat error!"<<endl;

exit(1);
}

cout<<"enter 10 integer numbers:"<<endl;

for(int i=0;i<10;i++)          //输入10个数存放到f1.dat文件中
{
cin>>a[i];

outfile1<<a[i]<<" ";
}

cout<<"enter 10 integer numbers:"<<endl;

for(int j=0;j<10;j++)           //输入10个数存放到f2.dat文件中
{
cin>>a[j];

outfile2<<a[j]<<" ";
}

outfile1.close();               //关闭f1.dat文件

outfile2.close();               //关闭f2.dat文件
}
//从f1,dat读入10个数，然后存放到f2.dat文件原有数据的后面
void fun2()
{
ifstream infile("f1.dat");       //f1.dat作为输入文件

if(!infile)
{
cerr<<"open f1.dat error!"<<endl;

exit(1);
}

ofstream outfile("f2.dat",ios::app);

//f2.dat作为输出文件，文件指针指向文件尾，向它写入的数据放在原来数据的后面
if(!outfile)
{
cerr<<"open f2.dat error!"<<endl;

exit(1);
}

int a;

for(int i=0;i<10;i++)
{
infile>>a;           //磁盘文件f2.dat读入一个整数

outfile<<a<<" ";     //将该数存放到f2.dat中
}

infile.close();

outfile.close();

//从f2.dat中读入20个整数，将它们按从小到大的顺序存放到f2.dat
void fun3()
{
ifstream infile("f2.dat"); //定义输入文件流infile，以输入方式打开f2.dat

if(!infile)
{
cerr<<"open f2.dat error!"<<endl;

exit(1);
}

int a[20];

int i,j,t;

for(i=0;i<20;i++)

infile>>a[i];        //从磁盘文件f2.dat读入20个数放在数组a中

for(i=0;i<19;i++)     //用起泡法对20个数排序

for(j=0;j<19-i;j++)

if(a[j]>a[j+1])

{t=a[j];a[j]=a[j+1];a[j+1]=t;}

infile.close();                //关闭输入文件f2.dat

ofstream outfile("f2.dat",ios::out);

// f2.dat作为输出文件，文件中原有内容删除
if(!outfile)
{
cerr<<"open f2.dat error!"<<endl;

exit(1);
}

cout<<"data in f2.dat:"<<endl;

for( i=0;i<20;i++)
{
outfile<<a[i]<<" ";      //向f2.dat输出已排序的20个数

cout<<a[i]<<" ";
}        //同时输出到显示器

cout<<endl;

outfile.close();
}

int main()
{
fun1();                     //分别调用3个函数

fun2();

fun3();

return 0;
}

#include <iostream>
#include <fstream>
using namespace std;
struct staff
{int num;
char name[20];
int age;
double  pay;
};
int main()
{staff staf[7]={3898,"Fan",34,1200,3899,"Wang",23,6740,2448,"Chen",54,778,
3000,"Du",45,4763,3301,"Ling",39,6555},staf1;
fstream iofile("staff.dat",ios::in|ios::out|ios::binary);
if(!iofile)
{cerr<<"open error!"<<endl;
abort();
}
int i,m,num;
cout<<"Five staff :"<<endl;
for(i=0;i<5;i++)
{cout<<staf[i].num<<" "<<staf[i].name<<" "<<staf[i].age<<" "<<staf[i].pay<<endl;
iofile.write((char *)&staf[i],sizeof(staf[i]));}
cout<<"please input data you want insert:"<<endl;
for(i=0;i<2;i++)
{cin>>staf1.num>>staf1.name>>staf1.age>>staf1.pay;
iofile.seekp(0,ios::end);
iofile.write((char *)&staf1,sizeof(staf1));}
iofile.seekg(0,ios::beg);
for(i=0;i<7;i++)
{iofile.read((char *)&staf[i],sizeof(staf[i]));
cout<<staf[i].num<<" "<<staf[i].name<<" "<<staf[i].age<<" "<<staf[i].pay<<endl;
}
bool find;
cout<<"enter number you want search,enter 0 to stop.";
cin>>num;
while(num)
{find=false;
iofile.seekg(0,ios::beg);
for(i=0;i<7;i++)
{iofile.read((char *)&staf[i],sizeof(staf[i]));
if(num==staf[i].num)
{m=iofile.tellg();
cout<<num<<" is No."<<m/sizeof(staf1)<<endl;
cout<<staf[i].num<<" "<<staf[i].name<<" "<<staf[i].age<<" "<<staf[i].pay<<endl;
find=true;
break;
}
}
if(!find)
cout<<"can't find "<<num<<endl;
cout<<"enter number you want search,enter 0 to stop.";
cin>>num;
}
iofile.close();
return 0;
}

#include <iostream>
#include <strstream>
using namespace std;

struct student
{
int num;

char name[20];

double score;
};

int main()
{
student stud[3]={1001,"Li",78,1002,"Wang",89.5,1004,"Fun",90},stud1[3];

char c[50];

int i;

ostrstream strout(c,50);

for(i=0;i<3;i++)
{
strout<<stud[i].num<<" "<<stud[i].name<<" "<<stud[i].score<<" ";
}
strout<<ends;

cout<<"array c:"<<endl<<c<<endl<<endl;

istrstream strin(c,50);

for(i=0;i<3;i++)
{
strin>>stud1[i].num>>stud1[i].name>>stud1[i].score;
}

cout<<"data from array c to array stud1:"<<endl;

for(i=0;i<3;i++)
{
cout<<stud1[i].num<<" "<<stud1[i].name<<" "<<stud1[i].score<<endl;
}

cout<<endl;

return 0;
}