猜數字遊戲

 import java.io.*;  
 public class GuessNumber {  
  private int[] answerSet = new int[10*9*8*7];  
  public GuessNumber() {  
   int index=0;  
   for (int n1=0; n1<10; n1++) {  
    for (int n2=0; n2<10; n2++) {  
     if ( n2 == n1) continue;  
     for (int n3=0; n3<10; n3++) {  
      if (n3 == n2 || n3 == n1 ) continue;  
      for (int n4=0; n4<10; n4++) {  
       if ( n4==n1 || n4==n2 || n4==n3) continue;  
       answerSet[index++] = n1*1000+n2*100+n3*10+n4;  
      }  
     }  
    }  
   }  
   guess();  
  }  
  private void input(int number) {  
   System.out.print( transform(number) + ", ?A?B = ");  
   int a=0,b=0;  
   try {  
    BufferedReader br = new BufferedReader (new InputStreamReader (System.in));  
    String str = br.readLine();  
    while ( str.length() != 4 ) {  
     System.out.println("輸入錯誤, 格式為 ?A?B ");  
     System.out.print( transform(number) + ", ?A?B = ");  
     str = br.readLine();  
    }  
    a = str.charAt(0) - '0';  
    b = str.charAt(2) - '0';   
   }  
   catch (IOException e) {  
    System.out.println("輸入時發生不可預期的錯誤...");  
    System.exit(0);  
   }   
   if (a == 4) {  
    System.out.println("The answer is " + transform(number));   
    System.exit(0);  
   }  
   reduce(number,a,b);  
  }  
  private void guess() {  
   for (int i=0; i< answerSet.length; i++) {  
    if ( answerSet[i] == -1 ) continue;  
    input ( answerSet[i]);  
   }  
   System.out.println("你騙人!! 根本沒這數字, ***!");  
  }  
  private void reduce(int number, int a, int b) {  
   for (int i=0; i< answerSet.length; i++) {  
    if ( answerSet[i] == -1) continue;  
    if (getA(number,answerSet[i]) != a || getB(number,answerSet[i]) != b )  
     answerSet[i] = -1;  
   }  
   for (int i=0; i < answerSet.length; i++) {  
    if ( answerSet[i] == -1) continue;  
    System.out.print( transform(answerSet[i]) + " ");  
   }   
   System.out.println();   
  }  
  private int getA(int n1, int n2) {  
   int a=0;  
   String str1 = transform(n1);  
   String str2 = transform(n2);  
   for (int i=0; i<4; i++) {  
    if (str1.charAt(i) == str2.charAt(i) )  
     a++;  
   }  
   return a;  
  }    private String transform (int n) {  
   if ( n < 1000 )  
    return "0" + n;  
   else  
    return ""+n;  
  }  
  private int getB(int n1, int n2) {  
   int b = 0;  
   String str1 = transform(n1);  
   String str2 = transform(n2);  
   for (int i=0; i < 4; i++) {  
    for (int j=0; j<4 ; j++) {  
     if ( i == j) continue;  
     if ( str1.charAt(i) == str2.charAt(j) )  
      b++;  
    }  
   }  
   return b;  
  }  
  public static void main (String [] args) {  
   GuessNumber app = new GuessNumber();  
  }  
 }  

參考來源