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前序遍历: 先输出父节点,再遍历左子树和右子树
中序遍历: 先遍历左子树,再输出父节点,再遍历右子树 后序遍历: 先遍历左子树,再遍历右子树,最后输出父节点 看输出父节点的顺序,就确定是前序,中序还是后序
对下面二叉树进行前中后续遍历和查找及节点的删除
package com.whb.tree;public class BinaryTreeDemo { public static void main(String[] args) { // 先需要创建一颗二叉树 BinaryTree binaryTree = new BinaryTree(); // 创建需要的结点 HeroNode root = new HeroNode(1, "宋江"); HeroNode node2 = new HeroNode(2, "吴用"); HeroNode node3 = new HeroNode(3, "卢俊义"); HeroNode node4 = new HeroNode(4, "林冲"); HeroNode node5 = new HeroNode(5, "关胜"); // 先手动创建该二叉树 root.setLeft(node2); root.setRight(node3); node3.setRight(node4); node3.setLeft(node5); binaryTree.setRoot(root); // 测试// System.out.println("前序遍历"); // 1,2,3,5,4// binaryTree.preOrder(); // 测试// System.out.println("中序遍历");// binaryTree.infixOrder(); // 2,1,5,3,4//// System.out.println("后序遍历");// binaryTree.postOrder(); // 2,5,4,3,1 // 前序遍历 // 前序遍历的次数 :4// System.out.println("前序遍历方式~~~");// HeroNode resNode = binaryTree.preOrderSearch(5);// if (resNode != null) { // System.out.printf("找到了,信息为 no=%d name=%s", resNode.getNo(), resNode.getName());// } else { // System.out.printf("没有找到 no = %d 的英雄", 5);// } // 中序遍历查找 // 中序遍历3次// System.out.println("中序遍历方式~~~");// HeroNode resNode = binaryTree.infixOrderSearch(5);// if (resNode != null) { // System.out.printf("找到了,信息为 no=%d name=%s", resNode.getNo(), resNode.getName());// } else { // System.out.printf("没有找到 no = %d 的英雄", 5);// } // 后序遍历查找 // 后序遍历查找的次数 2次// System.out.println("后序遍历方式~~~");// HeroNode resNode = binaryTree.postOrderSearch(5);// if (resNode != null) { // System.out.printf("找到了,信息为 no=%d name=%s", resNode.getNo(), resNode.getName());// } else { // System.out.printf("没有找到 no = %d 的英雄", 5);// } // 测试删除结点 System.out.println("删除前,前序遍历"); binaryTree.preOrder(); // 1,2,3,5,4 binaryTree.delNode(5); // binaryTree.delNode(3); System.out.println("删除后,前序遍历"); binaryTree.preOrder(); // 1,2,3,4 }}class BinaryTree{ private HeroNode root; public void setRoot(HeroNode root){ this.root = root; } // 删除结点 public void delNode(int no){ if (root != null){ if (root.getNo() == no){ root = null; }else { root.delNode(no); } }else { System.out.println("空树, 不能删除~"); } } //前序遍历 public void preOrder() { if(this.root != null) { this.root.preOrder(); }else { System.out.println("二叉树为空,无法遍历"); } } // 中序遍历 public void infixOrder(){ if (this.root != null){ this.root.infixOrder(); }else { System.out.println("二叉树为空"); } } // 后序遍历 public void postOrder(){ if (this.root != null){ this.root.postOrder(); }else { System.out.println("二叉树为空,无法遍历"); } } // 前序遍历查找 public HeroNode preOrderSearch(int no) { if(root != null) { return root.preOrderSearch(no); } else { return null; } } // 中序遍历查找 public HeroNode infixOrderSearch(int no) { if(root != null) { return root.infixOrderSearch(no); }else { return null; } } // 后序遍历查找 public HeroNode postOrderSearch(int no) { if(root != null) { return this.root.postOrderSearch(no); }else { return null; } }}class HeroNode{ private int no; private String name; private HeroNode left; private HeroNode right; public HeroNode(int no, String name){ this.no = no; this.name = name; } public int getNo() { return no; } public void setNo(int no) { this.no = no; } public String getName() { return name; } public void setName(String name) { this.name = name; } public HeroNode getLeft() { return left; } public void setLeft(HeroNode left) { this.left = left; } public HeroNode getRight() { return right; } public void setRight(HeroNode right) { this.right = right; } public String toString() { return "HeroNode [no=" + no + ", name=" + name + "]"; } // 递归删除节点 public void delNode(int no){ if (this.left != null && this.left.no == no){ this.left = null; return; } if (this.right != null && this.right.no == no){ this.right = null; return; } if (this.left != null){ this.left.delNode(no); } if (this.right != null){ this.right.delNode(no); } } // 前序遍历查找 public void preOrder(){ System.out.println(this); if(this.left != null){ this.left.preOrder(); } if(this.right != null){ this.right.preOrder(); } } // 中序遍历 public void infixOrder(){ if(this.left != null){ this.left.infixOrder(); } System.out.println(this); if(this.right != null){ this.right.infixOrder(); } } // 后序列遍历 public void postOrder(){ if (this.left != null){ this.left.postOrder(); } if(this.right != null){ this.right.postOrder(); } System.out.println(this); } // 前序遍历查找 public HeroNode preOrderSearch(int no){ System.out.println("进入前序遍历"); if (this.no == no){ return this; } HeroNode resNode = null; if (this.left != null){ resNode = this.left.preOrderSearch(no); } if (resNode != null){ return resNode; } if (this.right != null){ resNode = this.right.preOrderSearch(no); } return resNode; } // 中序遍历查找 public HeroNode infixOrderSearch(int no){ HeroNode resNode = null; if (this.left != null){ resNode = this.left.infixOrderSearch(no); } if (resNode != null){ return resNode; } System.out.println("进入中序查找"); if (this.no == no){ return this; } if (this.right != null){ resNode = this.right.infixOrderSearch(no); } return resNode; } // 后序遍历查找 public HeroNode postOrderSearch(int no){ HeroNode resNode = null; if (this.left != null){ resNode = this.postOrderSearch(no); } if (resNode != null){ return resNode; } if (this.right != null){ resNode = this.right.postOrderSearch(no); } if (resNode != null){ return resNode; } System.out.println("进入后序查找"); if (this.no == no){ resNode = this; } return resNode; }}
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