Java实现二叉搜索树

  这几天在看算法导论，昨晚上弄明白了二叉搜索树的一些操作和数据的组织结构。把伪代码转成Java来实现。

class Node {
Node leftChild;
Node rightChild;
Node parent;
int key;

public Node(int key) {
this.key = key;
}
}

class BinarySearchTree {
Node T = null;//树根

public void TREE_INSERT(Node z) {
Node y = null;
Node x = T;
while (x != null) {
y = x;//y总指向x的父节点
if (z.key < x.key)
x = x.leftChild;
else
x = x.rightChild;
}

z.parent = y;
if (y == null)//一开始是个空树
T = z;
else if (z.key < y.key)
y.leftChild = z;
else
y.rightChild = z;
}

public Node TREE_SEARCH(Node x, int k) {
if (x == null || k == x.key)
return x;
if (k < x.key)
return TREE_SEARCH(x.leftChild, k);
else
return TREE_SEARCH(x.rightChild, k);
}

public Node TREE_MINIMUM(Node x) {
while (x.leftChild != null)
x = x.leftChild;
return x;
}

public Node TREE_MAXIMUM(Node x) {
while (x.rightChild != null)
x = x.rightChild;
return x;
}

public Node TREE_SUCCESSOR(Node x) {
if (x.rightChild != null)
return TREE_MINIMUM(x.rightChild);
Node y = x.parent;
while (y != null && x == y.rightChild) {
x = y;
y = y.parent;
}
return y;
}

public Node TREE_DELETE(Node z) {
Node x, y;
if (z.leftChild == null || z.rightChild == null)
y = z;
else//左右子树的都有
y = TREE_SUCCESSOR(z);//求z的后继
if (y.leftChild != null)
x = y.leftChild;
else
x = y.rightChild;

if (x != null)
x.parent = y.parent;//z有两个子女的情况，x是y的左子树或右子树，y要么是z要么是z的后继

if (y.parent == null)
T = x;
else if (y == y.parent.leftChild)
y.parent.leftChild = x;
else
y.parent.rightChild = x;

if (y != z)
z.key = y.key;
return y;
}

public void TREE_SEARCH_SHOW(Node x) {
if (x == null)
return;
TREE_SEARCH_SHOW(x.leftChild);
System.out.print(x.key + " ");
TREE_SEARCH_SHOW(x.rightChild);
}
}

public class Main {
public static void main(String[] args) {
BinarySearchTree tree = new BinarySearchTree();
tree.TREE_INSERT(new Node(2));
tree.TREE_INSERT(new Node(3));
tree.TREE_INSERT(new Node(4));
Node node6 = new Node(6);
tree.TREE_INSERT(node6);
tree.TREE_INSERT(new Node(7));
tree.TREE_INSERT(new Node(9));
Node node13 = new Node(13);
tree.TREE_INSERT(node13);
tree.TREE_INSERT(new Node(15));
tree.TREE_INSERT(new Node(17));
tree.TREE_INSERT(new Node(18));
tree.TREE_INSERT(new Node(20));
System.out.println(tree.TREE_SUCCESSOR(node6).key);
System.out.println(tree.TREE_DELETE(node6).key);
tree.TREE_SEARCH_SHOW(tree.T);
}
}