我将尝试使用Cormen的伪代码实现二叉搜索树算法，但是遇到了问题。
以下是我节点的代码：
主要问题在于删除部分，有时按预期工作，有时错误删除，有时出现空指针异常。可能的问题是什么？
注：这不是作业。
以下是我节点的代码：
public class Node {
Node left;
Node right;
int value;
Node(int value){
this.value = value;
this.left = null;
this.right = null;
}
}
并且对于Bstree：
public class Btree {
Node root;
Btree(){
this.root = null;
}
public static void inorderWalk(Node n){
if(n != null){
inorderWalk(n.left);
System.out.print(n.value + " ");
inorderWalk(n.right);
}
}
public static Node getParent(Btree t, Node n){
Node current = t.root;
Node parent = null;
while(true){
if (current == null)
return null;
if( current.value == n.value ){
break;
}
if (current.value > n.value){
parent = current;
current = current.left;
}
else{ //(current.value < n.value)
parent = current;
current = current.right;
}
}
return parent;
}
public static Node search(Node n,int key){
if(n == null || key == n.value ){
return n;
}
if(key < n.value){
return search(n.left,key);
}
else{
return search(n.right,key);
}
}
public static Node treeMinimum(Node x){
if(x == null){
return null;
}
while(x.left != null){
x = x.left;
}
return x;
}
public static Node treeMaximum(Node x){
if(x == null){
return null;
}
while(x.right != null){
x = x.right;
}
return x;
}
public static Node treeSuccessor(Btree t,Node x){
if (x.right == null){
return treeMinimum(x.right);
}
Node y = getParent(t,x);
while(y != null && x == y.right){
x = y;
y = getParent(t,y);
}
return y;
}
public static Btree insert(Btree t,Node z){
Node y = null;
Node x = t.root;
while(x != null){
y = x;
if(z.value < x.value)
x = x.left;
else
x = x.right;
}
Node tmp = getParent(t,z);
tmp = y;
if(y == null){
t.root = z;
}
else if(z.value < y.value)
y.left = z;
else
y.right = z;
return t;
}
public static Btree delete(Btree t,Node z){
Node y,x;
if (z.left == null || z.right == null)
y = z;
else
y = treeSuccessor(t,z);
if (y.left != null)
x = y.left;
else
x = y.right;
if (x != null){
Node tmp = getParent(t,x);
tmp = getParent(t,y);
}
if (getParent(t,y) == null ){
t.root = x;
}
else{
if( y == getParent(t,y).left ){
getParent(t,y).left = x;
}
else{
getParent(t,y).right = x;
}
}
if(y != z){
z.value = y.value;
}
return t;
}
public static void main(String[] args){
Btree test = new Btree();
Node n1 = new Node(6);
Node n2 = new Node(3);
Node n3 = new Node(9);
Node n4 = new Node(1);
Node n5 = new Node(16);
Node n6 = new Node(4);
Node n7 = new Node(2);
Node n8 = new Node(11);
Node n9 = new Node(13);
test = insert(test,n1);
test = insert(test,n2);
test = insert(test,n3);
test = insert(test,n4);
test = insert(test,n5);
test = insert(test,n6);
test = insert(test,n7);
test = insert(test,n8);
test = insert(test,n9);
inorderWalk(test.root);
System.out.println();
test = delete(test,n8);
inorderWalk(test.root);
System.out.println();
test = delete(test,n5);
inorderWalk(test.root);
System.out.println();
test = delete(test,n2);
inorderWalk(test.root);
System.out.println();
test = delete(test,n1);
inorderWalk(test.root);
}
}
主要问题在于删除部分，有时按预期工作，有时错误删除，有时出现空指针异常。可能的问题是什么？
注：这不是作业。
if语句的“then”部分跟在同一行时才省略大括号。虽然不完美，但是是一个合理的折衷方案。将“then”部分编码在下面，缩进但没有大括号是你能做的最糟糕的事情。 - Carl Smotricz