caesarparse.cpp

Caesar加密方法

#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;
 string infileName,outfileName;
 cout<<"Input file name:";
 cin>>infileName;
 cout<<"Output file name:";
 cin>>outfileName;
 char ch;
 char temp;
 for(int i=1;i<26;i++)
 {
 OpenForInput(inFile,infileName);
 OpenForOutput(outFile,outfileName);
 
     while(inFile.get(ch))
	{
        cout<<ch;
        ch=tolower(ch);
        temp='a'+i;
	if(ch>='a'&&ch<temp)
            ch=ch+26-i;
        else if(ch>=temp&&ch<'z')
                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;
}