#include<iostream>#include<string>#include<fstream>using namespace std;ifstream in("密碼學.txt");void JiaMi(char ZhiHuan[]);   //加密函數void JieMi(char ZhiHuan[]);   //解密函數void setZhiHuan(char ZhiHuan[],char fanZhiHuanBiao[]);  //設置置換表函數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); //設置置換表 switch(m) //判斷m值，執行相應的功能 { 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;}