c++第一次作业

2-28

#include<iostream>
using namespace std;
int main(){
 char enter;
 cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:";
 while(cin>>enter)
 {
          if(enter=='A')
              cout<<"Data has been added!"<<endl;
          else if(enter=='D')
              cout<<"Data has been deleted!"<<endl;
          else if(enter=='S')
              cout<<"Data has been Sorted!"<<endl;
          else if(enter=='Q')
              break;
          else 
          cout<<"no such answer,please select one again!"<<endl;
          cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:";   
 }
         return 0; 
}
 
使用switch
#include<iostream>
using namespace std;
int main(){
          char enter;
          cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:";
           while(cin>>enter)
           {
                 switch(enter){
                 case 'A':cout<<"Data has been added!"<<endl;break;
                 case 'D':cout<<"Data has been deleted!"<<endl;break;
                 case 'S':cout<<"Data has been Sorted!"<<endl;break;
                case 'Q':break;
                 default:cout<<"no such answer,please select one again!"<<endl;
            }
            if(enter=='Q')
                  break;
     cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:"; 
    }
 return 0; 
}

2-29

（使用while）

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

int main()
{
                     int i=2,j=2,k=0;
                     while(i<=100){
                            while(j<=sqrt((double)i)){
                                    if(i%j==0)
                                         break;
                                         j++;
                                      }
                           if(j>sqrt((double)i))
                               {
                                  cout<<setw(5)<<i;
                                  if(++k%5==0)
                                       cout<<endl;
                                }
                          i++;j=2;
                        }
                         return 0;
}

(使用do while)

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{
 int i=2,j=2,k=0;
 do{
                do{
                    if(i%j==0)
                          break;
                          j++;
                     }while(j<=sqrt((double)i));
                 if(j>sqrt((double)i)){
                           cout<<setw(5)<<i;
                           if(++k%5==0)
                               cout<<endl;
                        }
                       i++;j=2;
        }while(i<=100);
 return 0;
}

(使用for循环)

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{
 int i,j,k=0;
     for(i=2;i<=100;i++)
{
     for(j=2;j<=sqrt((double)i);j++){
            if(i%j==0)
                break;
           }
            if(j>sqrt((double)i))
                   {
                       cout<<setw(5)<<i;
                       if(++k%5==0)
                               cout<<endl;
                   }
 }
 return 0;
}

 2-32

猜一个数字

（1）使用while

#include<iostream>
using namespace std;
#include<cstdlib>
#include<ctime>

int main(){
            srand((time(0)));
            int guessnumber=rand()%100+1;int guess;
            cout<<"please have a guess at number(1~100):";
            while(cin>>guess){
                     if(guess==guessnumber)
                            {
                               cout<<"you do it!"<<endl;
                               break;
                             }
                       else if(guess>guessnumber)
                       cout<<"your guess is larger than guessnumber!"<<endl;
                       else
                       cout<<"your guess is smaller than guessnumber!"<<endl;
                       cout<<"please have a guess at number(1~100):";
          }
return 0;
}

（2）使用 do...while

#include<iostream>
using namespace std;
#include<cstdlib>
#include<ctime> 
int main(){
           srand((time(0)));
           int guessnumber=rand()%100+1;
           int guess;
           cout<<"please have a guess at number(1~100):";
           cin>>guess;
           do{
                 if(guess==guessnumber)
                      {
                          cout<<"you do it!"<<endl;
                          break;
                      }
                 else if(guess>guessnumber)
                       cout<<"your guess is larger than guessnumber!"<<endl;
                 else
                       cout<<"your guess is smaller than guessnumber!"<<endl;
                       cout<<"please have a guess at number(1~100):";      
            }while(cin>>guess);
return 0;
}

2-34

（1）五种颜色取三个，10个的情况。

#include<iostream>
using namespace std;
enum colour{red,yellow,blue,white,black};
void print(int);         //it is used to transform int to colour and then output
int main()
{
 int x,y,z,k=0;
 for(x=red;x<=black;x++)
     for(y=x+1;y<=black;y++)
       for(z=y+1;z<=black;z++)
           {   
               {         
                   print(x);
                    cout<<" ";
                    print(y);
                    cout<<" ";
                    print(z);
                    cout<<endl;
                 }//it is used to printf x,y,z;
              k++;
           } 
  cout<<k;
 return 0;
}
void print(int x){
 switch(x)
 {
  {case 0:cout<<"red";break;}
  {case 1:cout<<"yellow";break;}
  {case 2:cout<<"blue";break;}
  {case 3:cout<<"white";break;}
  {case 4:cout<<"black";break;}
 }
}

（2）有顺序的情况 ，60

#include<iostream>
using namespace std;
enum colour{red,yellow,blue,white,black};
void print(int);//it is used to transform int to colour and then output
int main()
{
 int x,y,z,k=0;
 for(x=red;x<=black;x++)
      for(y=red;y<=black;y++)
      {  
         if(y==x)   continue;
         for(z=red;z<=black;z++)
             {
              if(z==x||z==y)
                continue;
                    {
                    print(x);
                    cout<<" ";
                    print(y);
                    cout<<" ";
                    print(z);
                    cout<<endl;
                    }//it is used to printf x,y,z;
              k++;
            }
    }
    cout<<k;
 return 0;
}
void print(int x){
 switch(x)
 {
  {case 0:cout<<"red";break;}
  {case 1:cout<<"yellow";break;}
  {case 2:cout<<"blue";break;}
  {case 3:cout<<"white";break;}
  {case 4:cout<<"black";break;}
 }
}

 总结：在第一次实验的过程中，我学会了如何去使用devc，已经codeblocks等一些软件，也初步对c++这个语言有了一些了解，在这个过程中，也在不断地解决问题和学习中学到了新的知识，比如说随机数，枚举型的使用。

https://www.cnblogs.com/mxueyyqx/

https://www.cnblogs.com/aiyy492903331/

https://www.cnblogs.com/sora5934/

https://www.cnblogs.com/qiuqiuwr/