问：在二叉树中搜索节点的程序。

2025年3月17日 | 阅读 7 分钟

树是一种非线性数据结构，以层次化的方式存储数据。树是由称为节点的元素集合组成。节点通过边连接并包含数据。树的第一个节点称为根。每个节点可以有或没有子节点。没有子节点的节点称为叶子节点。

二叉树是另一种类型的树数据结构，其中每个节点最多可以有两个子节点。也就是说，二叉树中的每个节点将包含数据、左子节点和右子节点。

Program to search a node in a Binary Tree

上图表示一个二叉树，其中 1 是树的根节点。节点 2 以 4 作为其左子节点，节点 3 以 5 作为其左子节点，以 6 作为其右子节点。节点 4、5 和 6 是叶子节点，因为它们没有子节点。

说明

在这个程序中，我们将搜索二叉树中一个特定值。如果存在，则打印消息“元素存在于二叉树中”，否则打印消息“元素不存在于二叉树中”。简而言之，我们将首先比较根节点的数据与要搜索节点的数据。如果找到匹配项，则将标志设置为 true。否则，在左子树中搜索节点，然后在右子树中搜索。

算法

定义 Node 类，它有三个属性：data、left 和 right。其中，left 表示节点的左子节点，right 表示节点的右子节点。
创建节点时，将数据传递给节点的 data 属性，并将 left 和 right 都设置为 null。
定义另一个类，该类有两个属性 root 和 flag。
1. Root 表示树的根节点，并将其初始化为 null。
2. Flag 将用于检查给定节点是否在树中。最初，它将设置为 false。
searchNode() 将在二叉树中搜索特定节点
1. 它检查根是否为空，这意味着树是空的。
2. 如果树不为空，它将比较 temp 的数据与值。如果它们相等，它将标志设置为true并返回。
3. 通过递归调用 searchNode() 来遍历左子树，并检查 value 是否存在于左子树中。
4. 通过递归调用 searchNode() 来遍历右子树，并检查 value 是否存在于右子树中。

解决方案

Python

#Represent a node of binary tree
class Node:
    def __init__(self,data):
        #Assign data to the new node, set left and right children to None
        self.data = data;
        self.left = None;
        self.right = None;
 
class SearchBinaryTree:
    def __init__(self):
        #Represent the root of binary tree
        self.root = None;
        self.flag = False;
    
    #searchNode() will search for the particular node in the binary tree
    def searchNode(self, temp, value):
        #Check whether tree is empty
        if(self.root == None):
            print("Tree is empty");
        
        else:
            #If value is found in the given binary tree then, set the flag to true
            if(temp.data == value):
                self.flag = True;
                return;
            
            #Search in left subtree
            if(self.flag == False and temp.left != None):
                self.searchNode(temp.left, value);
            
            #Search in right subtree
            if(self.flag == False and temp.right != None):
                self.searchNode(temp.right, value);
 
bt = SearchBinaryTree();
#Add nodes to the binary tree
bt.root = Node(1);
bt.root.left = Node(2);
bt.root.right = Node(3);
bt.root.left.left = Node(4);
bt.root.right.left = Node(5);
bt.root.right.right = Node(6);
        
#Search for node 5 in the binary tree
bt.searchNode(bt.root, 5);
 
if(bt.flag):
    print("Element is present in the binary tree");
else:
    print("Element is not present in the binary tree");

输出

Element is present in the binary tree

C

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
 
//Represent a node of binary tree
struct node{
    int data;
    struct node *left;
    struct node *right;
};
 
//Represent the root of binary tree
struct node *root = NULL;
 
static bool flag = false;
 
//createNode() will create a new node
struct node* createNode(int data){
    //Create a new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    //Assign data to newNode, set left and right children to NULL
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    
    return newNode;
}
 
//searchNode() will search for the particular node in the binary tree
void searchNode(struct node *temp, int value){
    //Check whether tree is empty
    if(root == NULL){
        printf("Tree is empty\n");
    }
    else{
        //If value is found in the given binary tree then, set the flag to true
        if(temp->data == value){
            flag = true;
             return;
        }
        //Search in left subtree
        if(flag == false && temp->left != NULL){
        searchNode(temp->left, value);
        }
        //Search in right subtree
        if(flag == false && temp->right != NULL){
        searchNode(temp->right, value);
        }
    }
}
 
int main()
{
    //Add nodes to the binary tree
    root = createNode(1);
    root->left = createNode(2);
    root->right = createNode(3);
    root->left->left = createNode(4);
    root->right->left = createNode(5);
    root->right->right = createNode(6);
        
    //Search for node 5 in the binary tree
    searchNode(root, 5);
    
    if(flag)
        printf("Element is present in the binary tree");
    else
        printf("Element is not present in the binary tree");
    return 0;
}

输出

Element is present in the binary tree

JAVA

public class SearchBinaryTree {
      
      //Represent a node of binary tree
      public static class Node{
        int data;
        Node left;
        Node right;
        
        public Node(int data){
          //Assign data to the new node, set left and right children to null
          this.data = data;
          this.left = null;
          this.right = null;
        }
      }
      
      //Represent the root of binary tree
      public Node root;
      
      public static boolean flag = false;
      
      public SearchBinaryTree(){
        root = null;
      }
      
      //searchNode() will search for the particular node in the binary tree
      public void searchNode(Node temp, int value){
        //Check whether tree is empty
        if(root == null){
          System.out.println("Tree is empty");
        }
        else{
          //If value is found in the given binary tree then, set the flag to true
          if(temp.data == value){
            flag = true;
               return;
          }
          //Search in left subtree
          if(flag == false && temp.left != null){
             searchNode(temp.left, value);
          }
          //Search in right subtree
          if(flag == false && temp.right != null){
             searchNode(temp.right, value);
          }
        }
      }
      
      public static void main(String[] args) {
       
        SearchBinaryTree bt = new SearchBinaryTree();
        //Add nodes to the binary tree
        bt.root = new Node(1);
        bt.root.left = new Node(2);
        bt.root.right = new Node(3);
        bt.root.left.left = new Node(4);
        bt.root.right.left = new Node(5);
        bt.root.right.right = new Node(6);
        
        //Search for node 5 in the binary tree
           bt.searchNode(bt.root, 5);
        
        if(flag)
          System.out.println("Element is present in the binary tree");
        else
          System.out.println("Element is not present in the binary tree");        
      }
    }

输出

Element is present in the binary tree

C#

using System; 
namespace Tree 
{                     
    public class Program
    {
        //Represent a node of binary tree
        public class Node<T>{
            public T data;
            public Node<T> left;
            public Node<T> right;
            
            public Node(T data) {
                //Assign data to the new node, set left and right children to null
                this.data = data;
                this.left = null;
                this.right = null;
            }
        }
        
        public class SearchBinaryTree<T>{
            //Represent the root of binary tree
            public Node<T> root;
 
            public static Boolean flag = false;
 
            public SearchBinaryTree(){
                root = null;
            }
        
            //searchNode() will search for the particular node in the binary tree
            public void searchNode(Node<T> temp, T value){
                //Check whether tree is empty
                if(root == null){
                  Console.WriteLine("Tree is empty");
                }
                else{
                    //If value is found in the given binary tree then, set the flag to true
                    if(temp.data.Equals(value)){
                        flag = true;
                        return;
                    }
                    //Search in left subtree
                    if(flag == false && temp.left != null){
                        searchNode(temp.left, value);
                    }
                    //Search in right subtree
                    if(flag == false && temp.right != null){
                         searchNode(temp.right, value);
                    }
                }
            }
        }
        
        public static void Main()
        {
            SearchBinaryTree<int> bt = new SearchBinaryTree<int>();
            //Add nodes to the binary tree
            bt.root = new Node<int>(1);
            bt.root.left = new Node<int>(2);
            bt.root.right = new Node<int>(3);
            bt.root.left.left = new Node<int>(4);
            bt.root.right.left = new Node<int>(5);
            bt.root.right.right = new Node<int>(6);
 
            //Search for node 5 in the binary tree
            bt.searchNode(bt.root, 5);
 
            if(SearchBinaryTree<int>.flag)
              Console.WriteLine("Element is present in the binary tree");
            else
              Console.WriteLine("Element is not present in the binary tree");
        }    
    }
}

输出

Element is present in the binary tree

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of binary tree
class Node{
    public $data;
    public $left;
    public $right;
    
    function __construct($data){
        //Assign data to the new node, set left and right children to NULL
        $this->data = $data;
        $this->left = NULL;
        $this->right = NULL;
    }
}
class SearchBinaryTree{
    //Represent the root of binary tree
    public $root;
    public $flag;
    function __construct(){
        $this->root = NULL;
        $this->flag = false;
    }
    
    //searchNode() will search for the particular node in the binary tree
    function searchNode($temp, $value){
        //Check whether tree is empty
        if($this->root == NULL){
          echo "Tree is empty<br>";
        }
        else{
          //If value is found in the given binary tree then, set the flag to true
          if($temp->data == $value){
              $this->flag = true;
              return;
          }
          //Search in left subtree
          if($this->flag == false && $temp->left != NULL){
              $this->searchNode($temp->left, $value);
          }
          //Search in right subtree
          if($this->flag == false && $temp->right != NULL){
              $this->searchNode($temp->right, $value);
          }
        }
    }
}
$bt = new SearchBinaryTree();
//Add nodes to the binary tree
$bt->root = new Node(1);
$bt->root->left = new Node(2);
$bt->root->right = new Node(3);
$bt->root->left->left = new Node(4);
$bt->root->right->left = new Node(5);
$bt->root->right->right = new Node(6);
 
//Search for node 5 in the binary tree
$bt->searchNode($bt->root, 5);
 
if($bt->flag)
    echo "Element is present in the binary tree";
else
    echo "Element is not present in the binary tree";      
?>
</body>
</html>

输出

Element is present in the binary tree

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