Java循環沒有做它應該做的事

Question

遞歸conflictCheck（）方法有問題。現在看來很好。我有測試打印線，看起來不錯。現在，當某些事情發生衝突（返回true）時，我的playChess（）方法應該通過調整節點的第二個變量來解決衝突，依此類推。

我的結果是字面上：

1,1

2,3

3,1

4,3

5,1 ...

即使輸出說「哦，我們有衝突」，它不會採取行動它一旦達到X，3

public static boolean conflictCheck(QueenNode a, QueenNode b) { 
    //checks for conflicts between head and all other nodes in the stack 
    if (b == null) { 
     System.out.println("Attempting Conflict Check: Nothing to Compare to"); 
     return false; 
    } 

    if (a.getRow()!=b.getRow() && a.getColumn()!=b.getColumn() && !diagonal(a,b)){ 
     System.out.println("Comparing " + a.getRow() + " ," + a.getColumn() + 
            " And " + b.getRow() + " , " + b.getColumn()); 
     conflictCheck(a,b.getNext()); 
    } 
    else { 
     System.out.println("There is a conflict with " +a.getRow() + "," + a.getColumn() 
          + " And " + b.getRow() + "," + b.getColumn()); 
     return true; 
     } 
    return false; 
} 


    public static void playChess() { 
    System.out.println("Playing chess"); 
    //Either there is a conflict between head and another node, the stack isn't full, or we have solution 
    if (conflictCheck(head, head.getNext())) { 
     if (head.getColumn() == 8) { 
      queens.pop(); 
     } 
     else if (!queens.isEmpty()) { 
      System.out.println("Adjusting head"); 
      head.setColumn(head.getColumn()+1); 
      System.out.println("Head is now " + head.getRow() + ", " + head.getColumn()); 
      playChess(); 

     } 
    } 

    else if (queens.size() < 8) { 
     System.out.println("Stack isn't full yet"); 
     queens.push(queens.size()+1,1); 
     queens.viewPieces(); 
     playChess(); 
     } 
    else { 
     success= true; 
     System.out.println("Success"); 
     queens.viewPieces(); 
     return; 
    } 
} 

整個輸出：

The stack 
1, 1 
End of stack 
Playing chess 
Attempting Conflict Check: Nothing to Compare to 
Stack isn't full yet 
The stack 
2, 1 
1, 1 
End of stack 
Playing chess 
There is a conflict with 2,1 And 1,1 
Adjusting head 
Head is now 2, 2 
Playing chess 
problem 
There is a conflict with 2,2 And 1,1 
Adjusting head 
Head is now 2, 3 
Playing chess 
Comparing 2 ,3 And 1 , 1 
Attempting Conflict Check: Nothing to Compare to 
Stack isn't full yet 
The stack 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
Comparing 3 ,1 And 2 , 3 
There is a conflict with 3,1 And 1,1 
Stack isn't full yet 
The stack 
4, 1 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
There is a conflict with 4,1 And 3,1 
Adjusting head 
Head is now 4, 2 
Playing chess 
problem 
There is a conflict with 4,2 And 3,1 
Adjusting head 
Head is now 4, 3 
Playing chess 
Comparing 4 ,3 And 3 , 1 
There is a conflict with 4,3 And 2,3 
Stack isn't full yet 
The stack 
5, 1 
4, 3 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
Comparing 5 ,1 And 4 , 3 
There is a conflict with 5,1 And 3,1 
Stack isn't full yet 
The stack 
6, 1 
5, 1 
4, 3 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
There is a conflict with 6,1 And 5,1 
Adjusting head 
Head is now 6, 2 
Playing chess 
problem 
There is a conflict with 6,2 And 5,1 
Adjusting head 
Head is now 6, 3 
Playing chess 
Comparing 6 ,3 And 5 , 1 
There is a conflict with 6,3 And 4,3 
Stack isn't full yet 
The stack 
7, 1 
6, 3 
5, 1 
4, 3 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
Comparing 7 ,1 And 6 , 3 
There is a conflict with 7,1 And 5,1 
Stack isn't full yet 
The stack 
8, 1 
7, 1 
6, 3 
5, 1 
4, 3 
3, 1 
2, 3 
1, 1 
End of stack 
Playing chess 
There is a conflict with 8,1 And 7,1 
Adjusting head 
Head is now 8, 2 
Playing chess 
problem 
There is a conflict with 8,2 And 7,1 
Adjusting head 
Head is now 8, 3 
Playing chess 
Comparing 8 ,3 And 7 , 1 
There is a conflict with 8,3 And 6,3 
Success 
The stack 
8, 3 
7, 1 
6, 3 
5, 1 
4, 3 
3, 1 
2, 3 
1, 1 
End of stack 

Answer 1

由於這是功課，有一個小提示：

您不要在衝突採取行動的理由您發現的原因很可能是因爲您忽略了從boolean conflictCheck(QueenNode a, QueenNode b)遞歸調用的返回值conflictCheck(a,b.getNext());。

第012頁的this excellent work by E.W.Dijkstra深入探討了八個女王的問題。它使用ALGOL-60編碼（甚至在我的時間之前就已經過時），但這些想法與語言無關。