实验2

2-28

（1）if....else

#include<iostream>
using namespace std;
int main()
{
	char choice;
	while(1)
	{
		cout<<"Menu:A(dd) D(elete) S(ort) Q(uit),Select one"<<endl;
		do {
			cin >> choice;
			if (choice != 'A' && choice != 'D' && choice != 'S' && choice != 'Q')
			{
				cout << "Input error,please re-enter." << endl;
			}
		} while (choice != 'A' && choice != 'D' && choice != 'S' && choice != 'Q');
		if(choice=='A')
		{
			cout<<"The data has incresed."<<endl;
			continue;
		}
		else if(choice=='D')
		{
			cout<<"The data has deleted."<<endl;
			continue;
		}
		else if(choice=='S')
		{
			cout<<"The data has sorted."<<endl;
			continue;
		}
		else 
		{
			cout<<"End......."<<endl;
			break;
		}
	}
	return 0;
}

(2)switch

#include<iostream>
using namespace std;
int main()
{
	char choice;
	while(1)
	{
		cout << "Menu:A(add) D(elete) S(ort) Q(uit),Select one:";
		do {
			cin >> choice;
			if (choice != 'A' && choice != 'D' && choice != 'S' && choice != 'Q')
			{
				cout << "Input error,please re-enter." << endl;
			}
		} while (choice != 'A' && choice != 'D' && choice != 'S' && choice != 'Q');
		switch (choice)
		{
		case 'A':
			cout << "The data has been increased." << endl; break;
		case 'D':
			cout << "The data has been deleted." << endl; break;
		case 'S':
			cout << "The data has been sorted." << endl; break;
		case 'Q':
			break;
		}
		if (choice == 'Q')
		{
			break;
		}
	}
	return 0;
} 

2-29

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

2-32 猜数游戏

#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
	char choice;
	int aim;
	int num;
	while(1)
	{
		unsigned seed;
		cout<<"please enter an unsigned integer"<<endl;
		cin>>seed;
		srand(seed);
		aim=rand(); 
		cout<<"please input one number..."<<endl;
		cin>>num;
		while(1)
		{
			if(num>aim)
			{
				cout<<"bigger.."<<endl;
				cin>>num;
			}
			else if(num<aim)
			{
				cout<<"lowwer"<<endl;
				cin>>num;
			}
			else
			{
				break;
			}
		}
		cout<<"play again?(Y/N)"<<endl;
		cin>>choice;
		if(choice=='Y')
		{
			continue;
		}
		else
		{
			break;
		}
	}
	return 0;
}  

2-34 取球

#include<iostream>
using namespace std;
enum Color{red,yellow,bule,white,black 
};
int main()
{
	Color ball;
	int i,j,k,t,sum=0;
	for(i=red;i<=black;i++)
	{
		for(j=i+1;j<=black;j++)//避免出现重复 
		{
			if(i==j)
			{
				break;
			}
			for(k=j+1;k<=black;k++)//同上，避免重复 
			{
				if(k!=i&&k!=j)
				{
					sum+=1;
					for(t=0;t<3;t++)
					{
						switch(t)
						{
							case 0:
								ball=Color(i);break;
							case 1:
								ball=Color(j);break;
							case 2:
								ball=Color(k);break;
						}
						switch(ball)
						{
							case red:
								cout<<"red ";break;
							case yellow:
								cout<<"yellow ";break;
							case bule:
								cout<<"bule ";break;
							case white:
								cout<<"white ";break;
							case black:
								cout<<"black ";break; 
						}
					}
					cout<<"   "<<endl;
				}
			}
		}
	}
	cout<<"一共有"<<sum<<"种方法"<<endl; 
	return 0; 
}