Question

我一直在尝试用我的树程序修复这些问题。我正在尝试构建一个基于参考的AVL树，它将保持自己的平衡。下面的方法是给我堆栈溢出和Nullpointer异常。我显然需要研究我的调试技巧，但是你能给我的任何建议都非常感激。

public AVLNode balance(AVLNode r){
System.out.println("start of balance");
if (r.getBalance()==r.MORE_LEFT){ /* dont need to check if r.hasLeft after this
  statement because if it passes has more left then it must have
  at least a left node */
  //if the left node has more attachments either left or right ways
    if(r.getLeft().getBalance()!=r.EVEN){
      System.out.println("r,MORE_LEFT && nextLeft is uneven");
      //calculateBalance(r);
      r.setLeft(balance(r.getLeft()));
    }else{
      System.out.println("doing the shift for "+(String)r.getElement());
      AVLNode shift=new AVLNode(r.getKey(), r.getElement(), null, r.getRight(), r.getBalance());
      r=balance(r.getLeft());
      insert(r, shift);
    }
//else if the Right side has more of the unbalance
}else if (r.getBalance()==r.MORE_RIGHT){
  if(r.getRight().getBalance()!=r.EVEN){
    System.out.println("r.MORE_RIGHT && nextRight is uneven");
    r.setRight(balance(r.getRight()));
  }
  else{
    System.out.println("doing the shift for "+(String)r.getElement());
    AVLNode shift=new AVLNode(r.getKey(), r.getElement(), r.getLeft(), null, r.getBalance());
    r=balance(r.getRight());
    insert(r,shift);
  }
}
if (r.hasLeft()) {
  System.out.println("botom left if run");
  r.setLeft(balance(r.getLeft()));
}
if (r.hasRight()) {
  System.out.println("bottom right if run");
  r.setRight(balance(r.getRight()));
}
return r;

}

 public void calculateBalance(AVLNode r){
    if (r!=null) {
      if (!r.hasRight() && !r.hasLeft())
        r.setBalance(r.EVEN);
      else {
        int rDeep=0;
        int lDeep=0;
        if (r.hasRight()) {
          rDeep=depth(r.getRight());
          calculateBalance(r.getRight());
        }
        if (r.hasLeft()) {
          lDeep=depth(r.getLeft());
          calculateBalance(r.getLeft());
        }
        if (lDeep>=2+rDeep){
          System.out.println("Node "+(String)r.getElement()+" has balance MORE_LEFT");
          r.setBalance(r.MORE_LEFT);
        }
        else if (rDeep>=2+lDeep){
          System.out.println("Node "+(String)r.getElement()+" has balance MORE_RIGHT");
          r.setBalance(r.MORE_RIGHT);
        }
        else{
          System.out.println("Node "+(String)r.getElement()+" has balance EVEN");
          r.setBalance(r.EVEN);
        }
      }
    }else System.out.println("null passed to calculateBalance You got splainin!!!");
  }
public int depth(AVLNode r){
if(r==null) return 0;
int max=Math.max(1+depth(r.getLeft()), 1+depth(r.getRight()));
System.out.println(""+max);
return max;
 //the number that is greater
//two options, go left or right count both and chose the greater one

} 这是堆栈跟踪，显示我收到错误的位置：

Level 1: VR 
Level 2: US WQ 
Level 3: GX 
Level 4: QE 
balanced 1 times.
start of balance
r,MORE_LEFT && nextLeft is uneven
start of balance
doing the shift for US
start of balance
bottom right if run
start of balance
bottom right if run
start of balance
bottom right if run
start of balance
Exception in thread "main" java.lang.NullPointerException
    at AVLDictionary.balance(AVLDictionary.java:64)
    at AVLDictionary.balance(AVLDictionary.java:93)
    at AVLDictionary.balance(AVLDictionary.java:93)
    at AVLDictionary.balance(AVLDictionary.java:67)
    at AVLDictionary.insert(AVLDictionary.java:42)
    at DictionaryAdvancedTest.main(DictionaryAdvancedTest.java:36)

递归AVL树平衡方法

0 个答案: