二叉搜索树

10-08/src/BinarySearchTree.java

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+import javax.sound.midi.Soundbank;
+
+/**
+ * @ClassName BinarySearchTree
+ * 二叉搜索树
+ * @Author: K
+ * @create: 2019/10/8-18:44
+ **/
+public class BinarySearchTree {
+    public static class Node{
+        int key;
+        Node left;
+        Node right;
+
+        public Node(int key){
+            this.key = key;
+        }
+    }
+    private Node root = null;
+    /* 在搜索树中查找 key 值，若找到返回该节点，若未找到返回空节点
+    * 时间复杂度 O(log(N)) - O(N)  */
+    public Node search(int key){
+        Node cur = root;
+        while(cur != null){
+            if(key == cur.key){
+                return cur;
+            }else if(key > cur.key){
+                cur = cur.right;
+            }else{
+                cur = cur.left;
+            }
+        }
+        return null;
+    }
+    /* 插入数据区，若已经存在则不进行插入，否则插入*/
+    public boolean insert(int key){
+        // 如果该树是一个空节点，直接插入，即让该节点为 根结点 root
+        if(root == null){
+            root = new Node(key);
+            return true;
+        }
+        // 寻找 key 值的合理位置,若该值已有则插入失败
+        Node cur = root;
+        Node parent = null;
+        while(cur != null){
+            if(key == cur.key){
+                return false;
+            }else if(key < cur.key){
+                parent = cur;
+                cur = cur.left;
+            }else{
+                parent = cur;
+                cur = cur.right;
+            }
+        }
+        // 插入
+        Node node = new Node(key);
+        if(key > parent.key){
+            parent.right = node;
+        }else{
+            parent.left = node;
+        }
+        return true;
+    }
+    // 删除
+    public boolean remove(int key){
+        Node cur = root;
+        Node parent = null;
+        // 先找到待删除节点以及他的父亲节点
+        while(cur != null){
+            if(cur.key == key){// 找到，准备删除
+                removeNode(parent,cur);
+                return true;
+            }else if(key > cur.key){
+                parent = cur;
+                cur = cur.right;
+            }else{
+                parent = cur;
+                cur = cur.left;
+            }
+        }
+        return false;
+    }
+
+    private void removeNode(Node parent, Node cur) {
+        // 进行删除
+        if(cur.left == null){
+            if(cur == root){
+                root = cur.right;
+            }else if(cur == parent.left){
+                parent.left = cur.right;
+            }else{
+                parent.right = cur.right;
+            }
+        }else if(cur.right == null){
+            if(cur == root){
+                root = cur.left;
+            }else if(cur == parent.left){
+                parent.left = cur.left;
+            }else{
+                parent.right = cur.left;
+            }
+        }else{// 替换法：在右子树寻找最小的(或者左子树中最大的)
+            Node goatParent = cur;
+            Node goat = cur.right;
+            while(goat.left != null){
+                goatParent = goat;
+                goat = goat.left;
+            }
+            cur.key = goat.key;
+            // 判断 goat 是 goatParent 的左孩子还是右孩子
+            if(goat == goatParent.left){
+                goatParent.left = goat.right;
+            }else{
+                goatParent.right = goat.right;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        // 1.创建搜索树 2.随机插入数据 3.打印前序 + 中序 4.查找 5.删除
+        BinarySearchTree tree = new BinarySearchTree();
+        int[] trees = {3,9,7,4,1,6,2,8,5};
+        for(int i : trees) {
+            tree.insert(i);
+        }
+        System.out.println("插入重复数据");
+        System.out.println(tree.insert(5));
+        System.out.println("插入数据：");
+        System.out.println(tree.insert(10));
+        System.out.print("前序遍历：");
+        preOrder(tree.root);
+        System.out.print("中序遍历：");
+        inOrder(tree.root);
+        System.out.println("查找数据：");
+        System.out.println(tree.search(9).key);
+        System.out.println(tree.remove(5));
+    }
+
+    private static void inOrder(Node node) {
+        if(node != null){
+            inOrder(node.left);
+            System.out.print(node.key + " ");
+            inOrder(node.right);
+        }
+    }
+    private static void preOrder(Node node) {
+        if(node != null){
+            System.out.print(node.key + " ");
+            preOrder(node.left);
+            preOrder(node.right);
+        }
+    }
+
+}