按级别顺序插入二叉树

给定一棵二叉树和一个键，将键插入二叉树中按级别顺序可用的第一个位置。

这个想法是使用队列对给定的树进行迭代级顺序遍历。如果我们找到一个左孩子为空的节点，我们将新的键作为该节点的左孩子。否则，如果我们找到一个右孩子为空的节点，我们将新的键设为右孩子。我们继续遍历树，直到找到一个左或右孩子为空的节点。

C++

// C++ program to insert element in Binary Tree
#include 
#include 
using namespace std;
 
/* A binary tree node has data, pointer to left child
and a pointer to right child */
 
struct Node {
    int data;
    Node* left;
    Node* right;
};
 
/* Function to create a new node */
 
Node* CreateNode(int data)
{
    Node* newNode = new Node();
    if (!newNode) {
        cout << "Memory error\n";
        return NULL;
    }
    newNode->data = data;
    newNode->left = newNode->right = NULL;
    return newNode;
}
 
/* Function to insert element in binary tree */
 
Node* InsertNode(Node* root, int data)
{
    // If the tree is empty, assign new node address to root
    if (root == NULL) {
        root = CreateNode(data);
        return root;
    }
 
    // Else, do level order traversal until we find an empty
    // place, i.e. either left child or right child of some
    // node is pointing to NULL.
    queue q;
    q.push(root);
 
    while (!q.empty()) {
        Node* temp = q.front();
        q.pop();
 
        if (temp->left != NULL)
            q.push(temp->left);
        else {
            temp->left = CreateNode(data);
            return root;
        }
 
        if (temp->right != NULL)
            q.push(temp->right);
        else {
            temp->right = CreateNode(data);
            return root;
        }
    }
}
 
/* Inorder traversal of a binary tree */
 
void inorder(Node* temp)
{
    if (temp == NULL)
        return;
 
    inorder(temp->left);
    cout << temp->data << ' ';
    inorder(temp->right);
}
 
// Driver code
int main()
{
    Node* root = CreateNode(10);
    root->left = CreateNode(11);
    root->left->left = CreateNode(7);
    root->right = CreateNode(9);
    root->right->left = CreateNode(15);
    root->right->right = CreateNode(8);
 
    cout << "Inorder traversal before insertion: ";
    inorder(root);
    cout << endl;
 
    int key = 12;
    root = InsertNode(root, key);
 
    cout << "Inorder traversal after insertion: ";
    inorder(root);
    cout << endl;
 
    return 0;
}

Java

// Java program to insert element in binary tree
import java.util.LinkedList;
import java.util.Queue;
public class GFG {
 
    /* A binary tree node has key, pointer to
    left child and a pointer to right child */
    static class Node {
        int key;
        Node left, right;
 
        // constructor
        Node(int key)
        {
            this.key = key;
            left = null;
            right = null;
        }
    }
    static Node root;
    static Node temp = root;
 
    /* Inorder traversal of a binary tree*/
    static void inorder(Node temp)
    {
        if (temp == null)
            return;
 
        inorder(temp.left);
        System.out.print(temp.key + " ");
        inorder(temp.right);
    }
 
    /*function to insert element in binary tree */
    static void insert(Node temp, int key)
    {
 
        if (temp == null) {
            root = new Node(key);
            return;
        }
        Queue q = new LinkedList();
        q.add(temp);
 
        // Do level order traversal until we find
        // an empty place.
        while (!q.isEmpty()) {
            temp = q.peek();
            q.remove();
 
            if (temp.left == null) {
                temp.left = new Node(key);
                break;
            }
            else
                q.add(temp.left);
 
            if (temp.right == null) {
                temp.right = new Node(key);
                break;
            }
            else
                q.add(temp.right);
        }
    }
 
    // Driver code
    public static void main(String args[])
    {
        root = new Node(10);
        root.left = new Node(11);
        root.left.left = new Node(7);
        root.right = new Node(9);
        root.right.left = new Node(15);
        root.right.right = new Node(8);
 
        System.out.print(
            "Inorder traversal before insertion:");
        inorder(root);
 
        int key = 12;
        insert(root, key);
 
        System.out.print(
            "\nInorder traversal after insertion:");
        inorder(root);
    }
}
// This code is contributed by Sumit Ghosh

Python3

# Python program to insert element in binary tree
class newNode():
 
    def __init__(self, data):
        self.key = data
        self.left = None
        self.right = None
         
""" Inorder traversal of a binary tree"""
def inorder(temp):
 
    if (not temp):
        return
 
    inorder(temp.left)
    print(temp.key,end = " ")
    inorder(temp.right)
 
 
"""function to insert element in binary tree """
def insert(temp,key):
 
    if not temp:
        root = newNode(key)
        return
    q = []
    q.append(temp)
 
    # Do level order traversal until we find
    # an empty place.
    while (len(q)):
        temp = q[0]
        q.pop(0)
 
        if (not temp.left):
            temp.left = newNode(key)
            break
        else:
            q.append(temp.left)
 
        if (not temp.right):
            temp.right = newNode(key)
            break
        else:
            q.append(temp.right)
     
# Driver code
if __name__ == '__main__':
    root = newNode(10)
    root.left = newNode(11)
    root.left.left = newNode(7)
    root.right = newNode(9)
    root.right.left = newNode(15)
    root.right.right = newNode(8)
 
    print("Inorder traversal before insertion:", end = " ")
    inorder(root)
 
    key = 12
    insert(root, key)
 
    print()
    print("Inorder traversal after insertion:", end = " ")
    inorder(root)
 
# This code is contributed by SHUBHAMSINGH10

C#

// C# program to insert element in binary tree
using System;
using System.Collections.Generic;
 
class GFG {
 
    /* A binary tree node has key, pointer to
    left child and a pointer to right child */
    public class Node {
        public int key;
        public Node left, right;
 
        // constructor
        public Node(int key)
        {
            this.key = key;
            left = null;
            right = null;
        }
    }
    static Node root;
 
    /* Inorder traversal of a binary tree*/
    static void inorder(Node temp)
    {
        if (temp == null)
            return;
 
        inorder(temp.left);
        Console.Write(temp.key + " ");
        inorder(temp.right);
    }
 
    /*function to insert element in binary tree */
    static void insert(Node temp, int key)
    {
          if (temp == null) {
            root = new Node(key);
            return;
        }
        Queue q = new Queue();
        q.Enqueue(temp);
 
        // Do level order traversal until we find
        // an empty place.
        while (q.Count != 0) {
            temp = q.Peek();
            q.Dequeue();
 
            if (temp.left == null) {
                temp.left = new Node(key);
                break;
            }
            else
                q.Enqueue(temp.left);
 
            if (temp.right == null) {
                temp.right = new Node(key);
                break;
            }
            else
                q.Enqueue(temp.right);
        }
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        root = new Node(10);
        root.left = new Node(11);
        root.left.left = new Node(7);
        root.right = new Node(9);
        root.right.left = new Node(15);
        root.right.right = new Node(8);
 
        Console.Write(
            "Inorder traversal before insertion:");
        inorder(root);
 
        int key = 12;
        insert(root, key);
 
        Console.Write(
            "\nInorder traversal after insertion:");
        inorder(root);
    }
}
 
// This code is contributed by Rajput-Ji

Javascript

// javascript program to insert element in binary tree
 
    /*
     * A binary tree node has key, pointer to left child and a pointer to right
     * child
     */
class Node {
    constructor(val) {
        this.key = val;
        this.left = null;
        this.right = null;
    }
}
 
    var temp;
 
    /* Inorder traversal of a binary tree */
    function inorder(temp) {
        if (temp == null)
            return;
 
        inorder(temp.left);
        document.write(temp.key + " ");
        inorder(temp.right);
    }
 
    /* function to insert element in binary tree */
    function insert(temp , key) {
 
        if (temp == null) {
            root = new Node(key);
            return;
        }
        var q = [];
        q.push(temp);
 
        // Do level order traversal until we find
        // an empty place.
        while (q.length!=0) {
            temp = q.pop();
             
 
            if (temp.left == null) {
                temp.left = new Node(key);
                break;
            } else
                q.push(temp.left);
 
            if (temp.right == null) {
                temp.right = new Node(key);
                break;
            } else
                q.push(temp.right);
        }
    }
 
    // Driver code
        var root = new Node(10);
        root.left = new Node(11);
        root.left.left = new Node(7);
        root.right = new Node(9);
        root.right.left = new Node(15);
        root.right.right = new Node(8);
 
        document.write("Inorder traversal before insertion:");
        inorder(root);
 
        var key = 12;
        insert(root, key);
 
        document.write("<br\>Inorder traversal after insertion:");
        inorder(root);
 
// This code is contributed by umadevi9616

输出

Inorder traversal before insertion: 7 11 10 15 9 8 
Inorder traversal after insertion: 7 11 12 10 15 9 8