#include<iostream>
#include<string>
#include<fstream>
using namespace std;

ifstream in("密碼學.txt");

void JiaMi(char ZhiHuan[]);   //加密函數(shù)
void JieMi(char ZhiHuan[]);   //解密函數(shù)
void setZhiHuan(char ZhiHuan[],char fanZhiHuanBiao[]);  //設(shè)置置換表函數(shù)
int main()
{
 int m;    //確定是加密或解密？加密為1，解密為2
 char ZhiHuanBiao['z'+1];   //正向置換表，加密時用
 char fanZhiHuanBiao['Z'+1];  //反向置換表，解密時用
 cout<<"加密按輸入1，解密輸入2"<<endl;
 in>>m;    //讀入m
 setZhiHuan(ZhiHuanBiao, fanZhiHuanBiao); //設(shè)置置換表
 switch(m) //判斷m值，執(zhí)行相應的功能
 {
 case 1: JiaMi(ZhiHuanBiao);break;
 case 2: JieMi(fanZhiHuanBiao);break;
 default:break;
 }
 return 0;
}

void JiaMi(char ZhiHuan[]) //加密
{
 string MingWen;  //保存明文
 cout<<endl<<"請輸入明文：";
 getline(in,MingWen); //讀入明文
 cout<<MingWen<<endl;  
 cout<<"加密后的密文為："<<endl;
 for(int i=0; i<MingWen.length(); i++) //直接利用置換表輸出密文
 {
 if(MingWen[i]>='a' && MingWen[i]<='z')
 cout<<ZhiHuan[ MingWen[i] ];
 else cout<<MingWen[i];
 }
 cout<<endl;
}

void JieMi(char fanZhiHuan[])
{
 string MiWen;  //保存密文
 cout<<endl<<"請輸入密文：";
 getline(in,MiWen); //讀入密文
 cout<<MiWen<<endl;
 cout<<"解密后的明文為："<<endl;
 for(int i=0; i<MiWen.length(); i++) //直接利用反置換表輸出明文
 {
 if(MiWen[i]>='A' && MiWen[i]<='Z')
 cout<<fanZhiHuan[ MiWen[i] ];
 else cout<<MiWen[i];
 }
 cout<<endl;
}

void setZhiHuan(char ZhiHuanBiao[],char fanZhiHuanBiao[])
{
 int i;  //i和j是循環(huán)變量，除此之外沒有任何意義
 char j;
 string s;  //密鑰
 cout<<"請輸入密鑰（大寫）："; 
 getline(in,s); //讀入密鑰
 cout<<s<<endl; //輸出密鑰
 cout<<"置換表為："<<endl;
 string s1;    
 for(i = 0 ; i < s.length();i++) //對密鑰進行處理（去掉空格和重復的字符）
 {
 bool sign =0;  //標志變量
 if(s[i] >= 'A' && s[i] <='Z')
 {
 for(int j = 0; j < s1.length();j++)
 {
 if(s[i] == s1[j])
 {
  sign = 1;
  break;
 }
 }
 if(sign == 0) s1 = s1 + s[i];
 else sign = 0;
 }
 }
 for( j ='a';j<='z';j++)cout<<j<<" ";cout<<endl; //輸出小寫字母 從a到z 
 char ch='A';
 for( i = 'a' ;i <= 'z'; i++) //該循環(huán)利用密鑰得到置換表
 {
 if(i < 'a' + s1.length()) //前面直接用s1代替
 { 
 ZhiHuanBiao[i] = s1[i-'a'];  
 }
 else //后面將剩下的"貼"上去
 {
 
 for(int j = 'a'; j < 'a' + s1.length(); j++)
 {
 if(ch == ZhiHuanBiao[j])
 {
  ch++;
  j= 'a'; //每次都從頭開始搜索
  continue;
 }
 }
 ZhiHuanBiao[i] = ch;
  ch++;
 }
 cout<<ZhiHuanBiao[i]<<" "; //同時輸出置換表
 }
 cout<<endl;
 for( i='a'; i<= 'z'; i++) //該循環(huán)利用置換表得到反置換表
 {
 fanZhiHuanBiao[ ZhiHuanBiao[i] ] = i;
 }
 for( i='A'; i<= 'Z'; i++) //輸出反置換表
 {
 cout<< fanZhiHuanBiao[i] <<" ";
 }
 cout<<endl;
}