import java.util.Scanner;

public class replacement {


 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  System.out.println("請輸入帶加密的明文：");
  String plaintexts = sc.nextLine();
  int len = plaintexts.length() % 7 == 0 ? plaintexts.length() / 7 : (plaintexts.length() / 7) + 1;//定義二維數組是要用到，主要作用是確定二維數組中一維數組的個數
  char[] plaintext_char = new char[7 * len];//先將明文存入一維數組中，在后面再將其存入二維數組中
  char[][] arr = new char[len][7];//存放明文和解密后的明文的二維數組
  char[][] miwen = new char[len][7];//存放密文的二維數組
  char[] n=new char[7];//在解密過程中用來消掉多余的填充的0
  int[] key = {6, 3, 0, 4, 1, 5, 2};//加密秘鑰
  int[] transkey = {2, 4, 6, 1, 3, 5, 0};//解密秘鑰

  fill(plaintexts, plaintext_char, len, arr);
  encryption(len, miwen, arr, key);
  System.out.println("加密后的明文是：");
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < miwen[i].length; j++) {
    System.out.print(miwen[i][j]);
   }
  }//輸出密文
  System.out.println(" ");
  System.out.println("按下1解密或按其他任意鍵退出：");
  String a=sc.nextLine();
  if (a.equals("1")){
   decryption(n,len, miwen, arr, transkey,plaintexts);
   for (int i = 0; i < len; i++) {
    for (int j = 0; j < arr[i].length; j++) {
     System.out.print(arr[i][j]);
    }
   }
  }else {
   System.out.println("退出！");
  }//輸出明文或退出
 }

 public static void fill(String plaintexts, char[] plaintext_char, int len, char[][] arr) {
  for (int i = 0; i < plaintexts.length(); i++) {
   plaintext_char[i] = plaintexts.charAt(i);
  }//將輸入的字符串存入擴充好的一維數組中，此時數組長度已達到標準，但是多出來的填充為是'\0'
  for (int i = 0; i < plaintext_char.length; i++) {
   if (plaintext_char[i] == '\u0000') {
    plaintext_char[i] = '0';
   }//將字符串數組中的空字符'\0'替換為0
 for (int i = 0; i < len; i++) {
   for (int j = i * 7, k = 0; j < 7 * (i + 1) && k < 7; j++, k++) {
    arr[i][k] = plaintext_char[j];
   }
  }//將擴充后的明文存入二維數組中，每七個一個一維數組
 }

 public static void encryption(int len, char[][] miwen, char[][] arr, int[] key) {
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < 7; j++) {
    miwen[i][j] = arr[i][key[j]];
   }
  }
 }//加密方法
 public static void decryption(char[] n,int len, char[][] miwen, char[][] arr, int[] trankey,String plaintexts) {
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < 7; j++) {
    arr[i][j] = miwen[i][trankey[j]];
   }
  }
  for (int i = 0; i <7-(7*len-plaintexts.length()); i++) {
   n[i]=arr[arr.length-1][i];
  }//7-(7*len-plaintexts.length())是二維數組中最后一個一維數組中的非填充位的個數，將非填充位加到n中
  arr[len-1]=n;//用n取代二維數組中最后一個數組，相當于將填充的0消去
 }//解密方法
}