import java.util.Scanner;

public class Affine{
 public static void main(String[] args) {
 char[] form = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
  'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '0'
  , '1', '2', '3', '4', '5', '6', '7', '8', '9'};
 Scanner sc = new Scanner(System.in);
 System.out.println("請輸入待加密的明文：");
 String MingWen = sc.nextLine();
 MingWen=MingWen.toUpperCase();//將輸入的明文全部大寫
 final int K1 = 103;
 final int K2 = 103;
 final int K3 = 31;
 int [] cipherNum=new int[MingWen.length()];//用來存儲數(shù)字化的密文
 encryption(MingWen,form,K1,K2,cipherNum);
 decryption(form,MingWen,K2,K3,cipherNum);

 }
 public static void encryption(String MingWen,char[] form,int K1,int K2,int[] cipherNum){
 //第一步：將明文存入數(shù)組
 char[] pla=new char[MingWen.length()];
 for (int i = 0; i <MingWen.length() ; i++) {
  pla[i]=MingWen.charAt(i);
 }//已將明文存入字符數(shù)組pla中
 //第二步：通過腳標找到明文中每個字符對應(yīng)的數(shù)，參與加密運算
 int[] MingWenNumber=new int[pla.length];
 for (int i = 0; i <pla.length ; i++) {
  for (int j = 0; j <form.length ; j++) {
  if (form[j]==pla[i]) {
   MingWenNumber[i] = j;
  }
  }
 }
 //通過腳標將明文全部轉(zhuǎn)化為數(shù)字
 char[] cipher = new char[MingWen.length()];//cipher密碼數(shù)組 用來存儲密文
 for (int i = 0; i <MingWen.length() ; i++) {
  int a= Math.floorMod((K1*MingWenNumber[i]+K2),36);
  cipherNum[i]=a;
  cipher[i]=form[a];
  //計算密文并存入數(shù)組中
 }
 System.out.println("加密結(jié)果是：");
 System.out.println(cipher);
 }

 public static void decryption(char[] form,String Mingwen,int K2,int K3,int[] cipherNum){
 char[] JieMI=new char[Mingwen.length()];
 for (int i =0;i<Mingwen.length();i++){
  JieMI[i]=form[Math.floorMod(K3*(cipherNum[i]-K2),36)];
 }
 System.out.println("解密結(jié)果是：");
 System.out.println(JieMI);
 }
}