caesar密码.cpp

凯撒密码

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

const int MAX_LEN=100;
char str[MAX_LEN];

int main()
{
	cout<<"				Caesar密码"<<endl;
loop:cout<<"1.加密"<<endl;
	cout<<"2.解密"<<endl;
	cout<<"3.退出"<<endl;
	cout<<"请选择:";
	int choice;
	cin>>choice;
	if (choice==1)			//加密
	{
		system("cls");
		cout<<"请输入需要加密的明文(小写):";
		cin>>str;
		int len=strlen(str);
		for (int i=0;i<len;i++)
		{
			if (str[i]<=119)		str[i]=str[i]+3-32;
			else str[i]=str[i]-23-32;
		}
		cout<<"加密后的密文为:"<<str<<endl<<endl<<endl;
		goto loop;
	}
	if (choice==2)			//解密
	{
		system("cls");
		cout<<"请输入需要解密的密文(大写):";
		cin>>str;
		int len=strlen(str);
		for (int i=0;i<len;i++)
		{
			if (str[i]>=68)			str[i]=str[i]-3+32;
			else str[i]=str[i]+23+32;
		}
		cout<<"解密后的明文为:"<<str<<endl<<endl<<endl;
		goto loop;
	}
	else return 1;
}