caesarencryt.cpp

Caesar加密算法

#include<iostream>
#include<fstream>
#include<string>
#include<cctype>
using namespace std;
void OpenForOutput(ofstream& outPut,string filename);
void OpenForInput(ifstream& inPut,string filename);
int main()
{
 ofstream outFile;
 ifstream inFile;
 int i;
 string infileName,outfileName;
 cout<<"Input file name:";
 cin>>infileName;
 cout<<"Input the number the Caesar parameter:"<<endl;
 cin>>i;
 cout<<"Output file name:";
 cin>>outfileName;
 char ch;
 char temp;
 OpenForInput(inFile,infileName);
 OpenForOutput(outFile,outfileName);
 
     while(inFile.get(ch))
        {
        cout<<ch;
        ch=tolower(ch);
        temp='z'-i;
        if(ch>temp&&ch<='z')
            ch=ch-26+i;
        else if(ch>='a'&&ch<=temp)
                ch=ch+i;
        outFile<<ch;
        }
 inFile.close();
 outFile.close();
 return 0;
}
void OpenForOutput(ofstream& outPut,string filename)
{
 outPut.open(filename.c_str(),ios::app);
 if(!outPut)
   cout<<"Can\'t open "<<filename<<endl;
}
void OpenForInput(ifstream& inPut,string filename)
{
 inPut.open(filename.c_str());
 if(!inPut)
   cout<<"Can\'t open "<<filename<<endl;
}