C++第二章作业

1.(1)if...else 用法

#include <iostream>

#include <cstring>

using namespace std;

int main()

{

char X;

cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:"<<endl;

while(cin>>X){

if(X=='A')

cout<<"Data has been added"<<endl;

else if(X=='D')

cout<<"Data has been deleted"<<endl;

else if(X=='S')

cout<<"Data has been sorted"<<endl;

else if(X=='Q')

break;

else

cout<<"Data does not exist"<<endl;

}

return 0;

}

(2)switch 用法

#include <iostream>

using namespace std;

int main()

{

char X;

cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one:"<<endl;

while(cin>>X){

if(X=='Q')

break;

switch(X){

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;

default: cout<<"Data does not exist"<<endl;

break;

}

}

return 0;

}

2.（1）for 用法

#include<iostream>

#include<cmath>

using namespace std;

int main()

{

int i,j,k;

for(i=2;i<=100;i++)

{

k=sqrt((double)i);

for(j=2;j<=k;j++)

{

if(i%j==0)

break;

}

if(j>k)

cout<<i <<" ";

}

return 0;

}

（2）while 用法

#include<iostream>

#include<cmath>

using namespace std;

int main()

{

int i=2,j,k;

while(i<=100)

{

k=sqrt((double)i);

for(j=2;j<=k;j++)

{

if(i%j==0)

break;

}

if(j>k)

cout<<i <<" ";

i++;

}

return 0;

}

（3）do...while 用法

#include<iostream>

#include<cmath>

using namespace std;

int main()

{

int i=2,j,k;

do

{

k=sqrt((double)i);

for(j=2;j<=k;j++)

{

if(i%j==0)

break;

}

if(j>k)

cout<<i <<" ";

i++;

}while(i<=100);

return 0;

}

3.(1)while 用法

#include<iostream>

using namespace std;

int main()

{

int i=23,j;

cout<<"Guess the num between 1 and 100:"<<endl;

while(cin>>j)

{

if(j>i&&j<=100)

cout<<"bigger than the num"<<endl;

else if(j>=1&&j<i)

cout<<"lower than the num"<<endl;

else if(j==i)

cout<<"Congratulations! You're right."<<endl;

else

cout<<"Error"<<endl;

}

return 0;

}

（2）do...while 用法

#include<iostream>

using namespace std;

int main()

{

int i=23,j;

cout<<"Guess the num between 1 and 100:"<<endl;

do

{

if(j>i&&j<=100)

cout<<"bigger than the num"<<endl;

else if(j>=1&&j<i)

cout<<"lower than the num"<<endl;

else if(j==i)

cout<<"Congratulations! You're right."<<endl;

else

cout<<"Error"<<endl;

}while(cin>>j);

return 0;

}

4.

#include<iostream>

using namespace std;

int main()

{

cout<<"the ways to go together is ";

int i,sum=1;

for(i=5;i>=3;i--)

{

sum*=i;

}

for(i=3;i>=1;i--)

{

sum/=i;

}

cout <<sum;

return 0;

}