BinarySearchTree Implements(Java 实现的二叉搜索树算法)

二叉搜索树的删除算法的确是比较复杂的...画了一个删除算法的活动图,希望可以帮助到各位博友.

 

以下是关于二叉搜索树的代码,比较难懂的都在代码中有注释:

节点类:Node

 package selfimpr.datastruct.binarysearchtree; /** * * @author selfimpr * @mail lgg860911@yahoo.com.cn * @blog http://blog.youkuaiyun.com/lgg201 */ public class Node { public Node left; public Node right; public long value; public Node() { } public Node(long value) { this.value = value; } }

 

二叉搜索树类:BinarySearchTree

 package selfimpr.datastruct.binarysearchtree; /** * * @author selfimpr * @mail lgg860911@yahoo.com.cn * @blog http://blog.youkuaiyun.com/lgg201 */ public class BinarySearchTree { public Node root; public BinarySearchTree() { } public BinarySearchTree(long value) { root = new Node(value); } //向树中插入一个值为value的节点 public void insert(long value) { if(root == null) { root = new Node(value); return ; } Node current = root; Node parent; while(true) { parent = current; if(value < current.value) { current = current.left; if(current == null) { parent.left = new Node(value); return ; } } else { current = current.right; if(current == null) { parent.right = new Node(value); return ; } } } } //查找树中是否存在值为value的节点 public boolean search(long value) { Node current = root; while(current != null) { if(value < current.value) { current = current.left; continue; } if(value > current.value) { current = current.right; continue; } return true; } return false; } public boolean delete(long value) { //根节点value和目标value相等时,直接删除. if(value == root.value) { root = null; return true; } Node current = root; //当前节点 Node parent = null; //当前节点的父节点 boolean isLeft = false; //标记current是parent的左子树还是右子树 //查找value在树中对应的节点 while(current != null && value != current.value) { //改变parent引用 parent = current; if(value < current.value) { //value小于current.value时,current改变为current的left节点 current = current.left; isLeft = true; continue ; } if(value > current.value) { //value大于current.value时,current改变为current的right节点 current = current.right; isLeft = false; continue ; } } //如果current==null说明树中没有值为value的节点. if(current == null) { return false; } //此处以上的代码经检验是正确的.此时查找到的current的value为目标value //也就是说,此时的current是要删除的节点 if(current.left == null && current.right == null) { //current没有子节点, 直接根据isLeft将parent指向current的引用切断 if(isLeft) { parent.left = null; } else { parent.right = null; } } else if(current.left != null && current.right == null) { //current只有左子节点, 根据isLeft切断parent指向current的引用, //让它指向current的左子节点 if(isLeft) { parent.left = current.left; } else { parent.right = current.left; } } else if(current.left == null && current.right != null) { //current只有右子节点, 根据isLeft切断parent指向current的引用, //让它指向current的右子节点 if(isLeft) { parent.left = current.right; } else { parent.right = current.right; } } else { //以下代码是查找current的后继节点(current右子树中的最小值节点) //重构current的右子树的过程. Node subsequence; //后继节点 if(current.right.left == null) { //如果current.right.left为空,说明后继节点就是current.right subsequence = current.right; } else { //设置后继节点和后继节点父节点的初值. subsequence = current.right; //后继节点 Node previouSubsequence = current; //后继节点的父节点 while(subsequence.left != null) { //由于后继节点是最小值节点.而二叉搜索树当前节点的左子节点值 //总是小于当前节点,所以子树中的最后一个左子树的根就是后继节点 previouSubsequence = subsequence; subsequence = subsequence.left; } //重构右current的右子树. //后继节点的前一个节点断开与后继节点的引用, //指向后继节点的右子节点. //这里因为后继节点是最后一个左子树的根节点,所以一定不存在左子节点. //因此下面的代码能够保证树中数据的完整性. previouSubsequence.left = subsequence.right; subsequence.right = current.right; //至此,通过后继节点完成了对current的右子树的重构 } //由后继节点的左子节点指向current的左子树. subsequence.left = current.left; //至此,完成了对current子树的重构,下面的代码只是根据isLeft将其 //和parent节点链接起来,并切断parent和current的引用. if(isLeft) { parent.left = subsequence; } else { parent.right = subsequence; } } //删除完成, 返回true; return true; } //展示树中的数据. public void display() { display(root); System.out.println(); } //遍历树. private void display(Node node) { if(node == null) return ; display(node.left); System.out.print(node.value + " "); display(node.right); } }

 

单元测试类:BinarySearchTreeTest

package selfimpr.datastruct.binarysearchtree.test; import java.util.Random; import junit.framework.TestCase; import selfimpr.datastruct.binarysearchtree.BinarySearchTree; /** * * @author selfimpr * @mail lgg860911@yahoo.com.cn * @blog http://blog.youkuaiyun.com/lgg201 */ public class BinarySearchTreeTest extends TestCase { Random random = new Random(); public void testTree() { BinarySearchTree tree = new BinarySearchTree(); tree.insert(50); for(int i=0; i<100; i++) { tree.insert(random.nextInt(100)); } tree.display(); // int num = 0; // for(int i=0; i<1000; i++) { // num = random.nextInt(100); // System.err.println("Test number is: " + num + ";result: " + tree.search(num)); // } for(int i=0; i<1000; i++) { tree.delete(random.nextInt(100)); tree.display(); } } }

 

后面继续会有快速排序法的实现,队列相关的实现(双端队列, 基于数组的,基于链表的队列), 栈, 链表的相关实现(单链表,双链表, 双端链表, 回环链表等), 最后可能会有堆的实现和红黑树的实现都发到上面来,请各位参考指导.

 

二叉搜索树删除算法活动图: