实验一 第二章

#include<iostream>
using namespace std;
int main()
{ char a;
  cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:"<<endl;
  cin>>a;
  while(a)
  {
   if(a=='A')
        cout<<"数据已经增加"<<endl; 
   else if(a=='D')   
        cout<<"数据已经删除"<<endl;
   else if(a=='S')
        cout<<"数据已经排序"<<endl; 
   else if(a=='Q')
        break; 
   else
        cout<<"输入错误"<<endl; 
        
     cin>>a; 
  }
    
   return 0;
} 

2-28

实现一个简单的菜单程序，运行时显示“Menu：A(dd) D(elete） S（ort） Q（uit），Selete one：”提示用户输入。A表示增加，D表示删除，S表示排序，Q表示退出。输入为A、D、S时分别提示“数据已经增加、删除、排序。”，输入Q时程序结束。 （1）if...else...语句，break，continue控制

if else语句

#include<iostream>
using namespace std;
int main()
{ char a;
  cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:"<<endl;
  cin>>a;
  while(a)
  {
   if(a=='A')
        cout<<"Data has added"<<endl;
 else if(a=='D')  
        cout<<"Data has deleted"<<endl;
   else if(a=='S')
        cout<<"Data has sorted"<<endl;
   else if(a=='Q')
        break;
   else
        cout<<"error"<<endl;
       
     cin>>a;
  }
   
   return 0;
}

switch语句

#include <iostream>
using namespace std;
int main() {
    char a;
    while(true)
         {cout<<"Menu:A(dd)D(elete)S(ort)Q(uit),Select one:"<<endl;
          cin>>a;
          switch (a)
          {case 'A':{cout<<"data has added"<<endl;continue;}
          case 'D':{cout<<"data has deleted"<<endl;continue;}
          case 'S':{cout<<"data has sorted"<<endl;continue;}
          case 'Q':break;
          default:{cout<<"error"<<endl;continue;}
          }
          break; 
         }
    return 0;
}

2-29

用穷举法找出1~100间的质数并显示出来。

while语句

#include<iostream>
#include<math.h>
using namespace std;
int main()
{int i=2,j,n=0;
 while(i<=100)
      {j=2;
       while(j<=sqrt(i))
            {if(i%j==0)
               break;
             j++;
            }
       if(j>=sqrt(i)) 
         {cout<<i<<"\t";
          n++;
         }
       if(n%5==0&&n!=0)
         {n=0;
          cout<<endl;
         }
       i++; 
      }
 return 0;
}

do...while语句

#include<iostream>
#include<math.h>
using namespace std;
int main()
{int i=2,j,n=0;
 do{j=2;
    do{if(i%j==0)
       break;
       j++;
      }while(j<=sqrt(i));
    if(j>=sqrt(i)) 
      {cout<<i<<"\t";
       n++;
      }
    if(n%5==0&&n!=0)
      {n=0;
       cout<<endl;
      }
    i++; 
   }while(i<=99);
 return 0;
}

for语句

#include<iostream>
#include<math.h>
using namespace std;
int main()
{int i,j,n=0;
 for(i=2;i<=100;i++)
    {j=2;
     for(j=2;j<=sqrt(i);j++)
        {if(i%j==0)
         break;
        }
     if(j>=sqrt(i)) 
       {cout<<i<<"\t";
        n++;
       }
     if(n%5==0&&n!=0)
       {n=0;
        cout<<endl;
       }
    }
 return 0;
}

2-32

在程序中定义一个整型变量，赋以1~100的值，要求用户猜这个数，比较两个数的大小，把结果提示给用户，直到猜对为止。

 while语句

#include<iostream>
#include<cstdlib>
#include<ctime>
using namespace std;
int main()
{int a,b;
 srand(time(0));
 a=rand()%100;
 cin>>b;
 while (true)
 {if (a<b)
    {cout<<"smaller than the number:"<<endl;
     cin>>b;    
    }
  else if (a>b)
    {cout<<"bigger than the number"<<endl;
     cin>>b;    
    }
  else 
    {cout<<"Bingo!"<<endl;
     break;    
    }
 }
return 0;    
}

 

do...while语句

#include<iostream>
#include<cstdlib>
#include<ctime>
using namespace std;
int main()
{int a,b;
 srand(time(0));
 a=rand()%100;
 cin>>b;
 do
 {if (a<b)
    {cout<<"smaller than the number:"<<endl;
     cin>>b;    
    }
  else if (a>b)
    {cout<<"bigger than the number:"<<endl;
     cin>>b;    
    }
  else 
    {cout<<"Bingo!"<<endl;
     break;    
    }
 }while (true);
 return 0;
}

 

2-34

口袋中有红黄蓝白黑5种颜色的球若干个。没词葱口袋中取出3个颜色不同的球，问有多少种取法  

#include<iostream>
using namespace std;
int main()
{int i,j,k,t=0;
  cout<<"Red:0,Yellow:1,Blue:2;White:3,Black:4"<<endl;
  for(i=0;i<=4;i++)
  {for(j=i+1;j<=4;j++)
  {if(j==i)continue;
    for(k=j+1;k<=4;k++)
    {if(k==i||k==j) continue;
     cout<<i<<j<<k<<endl;
     t++;
    }
  }
  }
  cout<<"total:"<<t<<endl;
  return 0; 
 }