给定一个二叉树，任务是从中间到上-下顺序遍历该二叉树。
在从上到下的顺序遍历中，执行以下步骤：
- 首先，打印树的中间层。
- 然后，在树的中间层之上的一层上打印元素。
- 然后，在树的中间层下方的一层打印元素。
- 然后，在树的中间层上方的两个层上打印元素。
- 然后，在树的中间层下面的两个层上打印元素，依此类推。
注意：在这个问题中，中间电平被认为是在((H / 2)+ 1)个水平，其中H是树和根的液面的高度被认为是1。
例子：
Input:
10
/ \
12 13
/ \
14 15
/ \ / \
21 22 23 24
Output:
14, 15,
12, 13,
21, 22, 23, 24,
10,
Explanation:
There are 4 levels in the tree.
Therefore, Middle level = ((4 / 2) + 1) = 3
Now, the tree is traversed in the following way:
Middle level: 14, 15
One level above the middle level: 12, 13
One level below the middle level: 21, 22, 23, 24
Two levels above the middle level: 10
Input:
5
/ \
2 13
/ \ \
4 25 6
/ / \
11 3 21
\
9
Output:
4, 25, 6
2, 13
11, 3, 21
5
9
Explanation:
There are 5 levels in the tree.
Therefore, Middle level = ((5 / 2) + 1) = 3.
Now, the tree is traversed in the following way:
Middle level: 4, 25, 6
One level above the middle level: 2, 13
One level below the middle level: 11, 3, 21
Two levels above the middle level: 5
Two levels below the middle level: 9方法：想法是将树存储在矩阵中。为了做到这一点，
- 计算树的高度和宽度。
- 在计算高度和最大宽度之后，将创建一个2d矩阵，并在树上执行广度优先搜索，以将树存储在矩阵中。
例如：
- 然后，简单地遍历矩阵并根据给定条件从矩阵中打印值。
下面是上述方法的实现：
C++
// C++ program to traverse the tree
// from the middle to up and down
#include
using namespace std;
// A Tree node
struct Node {
int key;
struct Node *left, *right;
};
// Utility function to create
// a new node
Node* newNode(int key)
{
Node* temp = new Node;
temp->key = key;
temp->left = temp->right = NULL;
return (temp);
}
// Function to calculate the
// height of the tree
int findHeight(struct Node* node)
{
// Base condition
if (node == NULL)
return 0;
int leftHeight = findHeight(node->left);
int rightHeight = findHeight(node->right);
// Return the maximum of the height
// of the left and right subtree
return 1 + (leftHeight > rightHeight
? leftHeight
: rightHeight);
}
// Function to find the width of the tree
void findWidth(struct Node* node, int& maxValue,
int& minValue, int hd)
{
// Base cases
if (node == NULL)
return;
if (hd > maxValue) {
maxValue = hd;
}
if (hd < minValue) {
minValue = hd;
}
// Recursively call the function twice to find
// the maximum width
findWidth(node->left, maxValue, minValue, hd - 1);
findWidth(node->right, maxValue, minValue, hd + 1);
}
// Function to traverse the tree and
// store level order traversal in a matrix
void BFS(int** mtrx, struct Node* node)
{
// Create queue for storing
// the addresses of nodes
queue qu;
qu.push(node);
int i = -1, j = -1;
struct Node* poped_node = NULL;
// Iterating over the queue to perform
// breadth-first search traversal
while (!qu.empty()) {
i++;
int qsize = qu.size();
while (qsize--) {
j++;
poped_node = qu.front();
// Store the data of the node into
// the matrix
mtrx[i][j] = poped_node->key;
qu.pop();
// Performing BFS for the remaining
// nodes in the queue
if (poped_node->left != NULL) {
qu.push(poped_node->left);
}
if (poped_node->right != NULL) {
qu.push(poped_node->right);
}
}
j = -1;
}
}
// Function for Middle to Up Down
// Traversal of Binary Tree
void traverse_matrix(int** mtrx, int height,
int width)
{
// Variables to handle rows and columns
// of the matrix
int up = (height / 2);
int down = up + 1;
bool flag = true;
int k = 0;
// Print the middle row
for (int j = 0; j < width; j++) {
if (mtrx[up][j] != INT_MAX) {
cout << mtrx[up][j] << ", ";
}
}
cout << endl;
up--;
// Loop to print the remaining rows
for (int i = 0; i < (height - 1); i++) {
// Condition to manage up and
// down indices in the matrix
if (flag) {
k = up;
up--;
flag = !flag;
}
else {
k = down;
down++;
flag = !flag;
}
// Loop to print the value
// of matrix cells in perticular row
for (int j = 0; j < width; j++) {
if (mtrx[k][j] != INT_MAX) {
cout << mtrx[k][j] << ", ";
}
}
cout << endl;
}
}
// A utility function for middle to
// up down traversal
void printPattern(struct Node* node)
{
// max, min has been taken for
// calculating the width of tree
int max_value = INT_MIN;
int min_value = INT_MAX;
int hd = 0;
// Calculate the width of a tree
findWidth(node, max_value, min_value, hd);
int width = max_value + abs(min_value);
// Calculate the height of the tree
int height = findHeight(node);
// Double pointer to create 2D array
int** mtrx = new int*[height];
// Initialize the width for
// each row of the matrix
for (int i = 0; i < height; i++) {
mtrx[i] = new int[width];
}
// Initialize complete matrix with
// MAX INTEGER(purpose garbage)
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
mtrx[i][j] = INT_MAX;
}
}
// Store the BFS traversal of the tree
// into the 2-D matrix
BFS(mtrx, node);
// Print the circular clockwise spiral
// traversal of the tree
traverse_matrix(mtrx, height, width);
// release extra memory
// allocated for matrix
free(mtrx);
}
// Driver Code
int main()
{
/*
10
/ \
12 13
/ \
14 15
/ \ / \
21 22 23 24
*/
// Creating the above tree
Node* root = newNode(10);
root->left = newNode(12);
root->right = newNode(13);
root->right->left = newNode(14);
root->right->right = newNode(15);
root->right->left->left = newNode(21);
root->right->left->right = newNode(22);
root->right->right->left = newNode(23);
root->right->right->right = newNode(24);
printPattern(root);
return 0;
} Java
// Java program to traverse the tree
// from the middle to up and down
import java.util.*;
class GFG{
// A Tree node
static class Node {
int key;
Node left, right;
};
static int maxValue, minValue;
// Utility function to create
// a new node
static Node newNode(int key)
{
Node temp = new Node();
temp.key = key;
temp.left = temp.right = null;
return (temp);
}
// Function to calculate the
// height of the tree
static int findHeight(Node node)
{
// Base condition
if (node == null)
return 0;
int leftHeight = findHeight(node.left);
int rightHeight = findHeight(node.right);
// Return the maximum of the height
// of the left and right subtree
return 1 + (leftHeight > rightHeight
? leftHeight
: rightHeight);
}
// Function to find the width of the tree
static void findWidth(Node node, int hd)
{
// Base cases
if (node == null)
return;
if (hd > maxValue) {
maxValue = hd;
}
if (hd < minValue) {
minValue = hd;
}
// Recursively call the function twice to find
// the maximum width
findWidth(node.left, hd - 1);
findWidth(node.right, hd + 1);
}
// Function to traverse the tree and
// store level order traversal in a matrix
static void BFS(int [][]mtrx, Node node)
{
// Create queue for storing
// the addresses of nodes
Queue qu = new LinkedList();
qu.add(node);
int i = -1, j = -1;
Node poped_node = null;
// Iterating over the queue to perform
// breadth-first search traversal
while (!qu.isEmpty()) {
i++;
int qsize = qu.size();
while (qsize-- > 0) {
j++;
poped_node = qu.peek();
// Store the data of the node into
// the matrix
mtrx[i][j] = poped_node.key;
qu.remove();
// Performing BFS for the remaining
// nodes in the queue
if (poped_node.left != null) {
qu.add(poped_node.left);
}
if (poped_node.right != null) {
qu.add(poped_node.right);
}
}
j = -1;
}
}
// Function for Middle to Up Down
// Traversal of Binary Tree
static void traverse_matrix(int [][]mtrx, int height,
int width)
{
// Variables to handle rows and columns
// of the matrix
int up = (height / 2);
int down = up + 1;
boolean flag = true;
int k = 0;
// Print the middle row
for (int j = 0; j < width; j++) {
if (mtrx[up][j] != Integer.MAX_VALUE) {
System.out.print(mtrx[up][j]+ ", ");
}
}
System.out.println();
up--;
// Loop to print the remaining rows
for (int i = 0; i < (height - 1); i++) {
// Condition to manage up and
// down indices in the matrix
if (flag) {
k = up;
up--;
flag = !flag;
}
else {
k = down;
down++;
flag = !flag;
}
// Loop to print the value
// of matrix cells in perticular row
for (int j = 0; j < width; j++) {
if (mtrx[k][j] != Integer.MAX_VALUE) {
System.out.print(mtrx[k][j]+ ", ");
}
}
System.out.println();
}
}
// A utility function for middle to
// up down traversal
static void printPattern(Node node)
{
// max, min has been taken for
// calculating the width of tree
maxValue = Integer.MIN_VALUE;
minValue = Integer.MAX_VALUE;
int hd = 0;
// Calculate the width of a tree
findWidth(node, hd);
int width = maxValue + Math.abs(minValue);
// Calculate the height of the tree
int height = findHeight(node);
// Double pointer to create 2D array
int [][]mtrx = new int[width][height];
// Initialize complete matrix with
// MAX INTEGER(purpose garbage)
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
mtrx[i][j] = Integer.MAX_VALUE;
}
}
// Store the BFS traversal of the tree
// into the 2-D matrix
BFS(mtrx, node);
// Print the circular clockwise spiral
// traversal of the tree
traverse_matrix(mtrx, height, width);
// release extra memory
// allocated for matrix
mtrx =null;
}
// Driver Code
public static void main(String[] args)
{
/*
10
/ \
12 13
/ \
14 15
/ \ / \
21 22 23 24
*/
// Creating the above tree
Node root = newNode(10);
root.left = newNode(12);
root.right = newNode(13);
root.right.left = newNode(14);
root.right.right = newNode(15);
root.right.left.left = newNode(21);
root.right.left.right = newNode(22);
root.right.right.left = newNode(23);
root.right.right.right = newNode(24);
printPattern(root);
}
}
// This code is contributed by Rajput-Ji Python3
# Python3 program for the
# above approach
from collections import deque
# A Tree node
class Node:
def __init__(self, x):
self.key = x
self.left = None
self.right = None
minValue, maxValue = 0, 0
# Function to calculate the
# height of the tree
def findHeight(node):
# Base condition
if (node == None):
return 0
leftHeight = findHeight(node.left)
rightHeight = findHeight(node.right)
# Return the maximum of the height
# of the left and right subtree
if leftHeight > rightHeight:
return leftHeight + 1
return rightHeight + 1
# Function to find the width
# of the tree
def findWidth(node, hd):
global minValue, maxValue
# Base cases
if (node == None):
return
if (hd > maxValue):
maxValue = hd
if (hd < minValue):
minValue = hd
# Recursively call the
# function twice to find
# the maximum width
findWidth(node.left,
hd - 1)
findWidth(node.right,
hd + 1)
# Function to traverse the
# tree and store level order
# traversal in a matrix
def BFS(mtrx, node):
# Create queue for storing
# the addresses of nodes
qu = deque()
qu.append(node)
i = -1
j = -1
poped_node = None
# Iterating over the queue
# to perform breadth-first
# search traversal
while (len(qu) > 0):
i += 1
qsize = len(qu)
while (qsize):
j += 1
poped_node = qu.popleft()
# Store the data of the
# node into the matrix
mtrx[i][j] = poped_node.key
#qu.pop()
# Performing BFS for
# the remaining nodes
# in the queue
if (poped_node.left != None):
qu.append(poped_node.left)
if (poped_node.right != None):
qu.append(poped_node.right)
qsize -= 1
j = -1
#Function for Middle to Up Down
#Traversal of Binary Tree
def traverse_matrix(mtrx,
height,width):
# Variables to handle rows
# and columns of the matrix
up = (height // 2)
down = up + 1
flag = True
k = 0
# Print middle row
for j in range(width):
if (mtrx[up][j] != 10 ** 9):
print(mtrx[up][j], end = ", ")
print()
up -= 1
# Loop to prthe remaining rows
for i in range(height - 1):
# Condition to manage up and
# down indices in the matrix
if (flag):
k = up
up -= 1
flag = not flag
else:
k = down
down += 1
flag = not flag
# Loop to prthe value
# of matrix cells in
# particular row
for j in range(width):
if (mtrx[k][j] != 10 ** 9):
print(mtrx[k][j], end = ", ")
print()
# A utility function for middle to
# up down traversal
def printPattern(node):
global maxValue, minValue
# max, min has been taken for
# calculating the width of tree
maxValue = -10 ** 9
minValue = 10 ** 9
hd = 0
# Calculate the width
# of a tree
findWidth(node, hd)
width = maxValue + abs(minValue)
# Calculate the height of the tree
height = findHeight(node)
# print(height,width)
#Double pointer to create 2D array
mtrx = [[10 ** 9 for i in range(width + 1)]
for i in range(height + 1)]
# Store the BFS traversal of the tree
# into the 2-D matrix
BFS(mtrx, node)
# Print circular clockwise spiral
# traversal of the tree
traverse_matrix(mtrx, height, width)
# Driver Code
if __name__ == '__main__':
# /*
# 10
# / \
# 12 13
# / \
# 14 15
# / \ / \
# 21 22 23 24
# */
# Creating the above tree
root = Node(10)
root.left = Node(12)
root.right = Node(13)
root.right.left = Node(14)
root.right.right = Node(15)
root.right.left.left = Node(21)
root.right.left.right = Node(22)
root.right.right.left = Node(23)
root.right.right.right = Node(24)
printPattern(root)
# This code is contributed by Mohit Kumar 29C#
// C# program to traverse the tree
// from the middle to up and down
using System;
using System.Collections;
using System.Collections.Generic;
class GFG
{
// A Tree node
class Node
{
public int key;
public Node left, right;
};
static int maxValue, minValue;
// Utility function to create
// a new node
static Node newNode(int key)
{
Node temp = new Node();
temp.key = key;
temp.left = temp.right = null;
return (temp);
}
// Function to calculate the
// height of the tree
static int findHeight(Node node)
{
// Base condition
if (node == null)
return 0;
int leftHeight = findHeight(node.left);
int rightHeight = findHeight(node.right);
// Return the maximum of the height
// of the left and right subtree
return 1 + (leftHeight > rightHeight
? leftHeight
: rightHeight);
}
// Function to find the width of the tree
static void findWidth(Node node, int hd)
{
// Base cases
if (node == null)
return;
if (hd > maxValue) {
maxValue = hd;
}
if (hd < minValue) {
minValue = hd;
}
// Recursively call the function twice to find
// the maximum width
findWidth(node.left, hd - 1);
findWidth(node.right, hd + 1);
}
// Function to traverse the tree and
// store level order traversal in a matrix
static void BFS(int [,]mtrx, Node node)
{
// Create queue for storing
// the addresses of nodes
Queue qu = new Queue();
qu.Enqueue(node);
int i = -1, j = -1;
Node poped_node = null;
// Iterating over the queue to perform
// breadth-first search traversal
while (qu.Count != 0)
{
i++;
int qsize = qu.Count;
while (qsize-- > 0) {
j++;
poped_node = (Node)qu.Peek();
// Store the data of the node into
// the matrix
mtrx[i,j] = poped_node.key;
qu.Dequeue();
// Performing BFS for the remaining
// nodes in the queue
if (poped_node.left != null) {
qu.Enqueue(poped_node.left);
}
if (poped_node.right != null) {
qu.Enqueue(poped_node.right);
}
}
j = -1;
}
}
// Function for Middle to Up Down
// Traversal of Binary Tree
static void traverse_matrix(int [,]mtrx, int height,
int width)
{
// Variables to handle rows and columns
// of the matrix
int up = (height / 2);
int down = up + 1;
bool flag = true;
int k = 0;
// Print the middle row
for (int j = 0; j < width; j++) {
if (mtrx[up, j] != 100000000) {
Console.Write(mtrx[up,j]+ ", ");
}
}
Console.WriteLine();
up--;
// Loop to print the remaining rows
for (int i = 0; i < (height - 1); i++)
{
// Condition to manage up and
// down indices in the matrix
if (flag) {
k = up;
up--;
flag = !flag;
}
else {
k = down;
down++;
flag = !flag;
}
// Loop to print the value
// of matrix cells in perticular row
for (int j = 0; j < width; j++)
{
if (mtrx[k, j] != 100000000) {
Console.Write(mtrx[k,j]+ ", ");
}
}
Console.WriteLine();
}
}
// A utility function for middle to
// up down traversal
static void printPattern(Node node)
{
// max, min has been taken for
// calculating the width of tree
maxValue = -100000000;
minValue = 100000000;
int hd = 0;
// Calculate the width of a tree
findWidth(node, hd);
int width = maxValue + Math.Abs(minValue);
// Calculate the height of the tree
int height = findHeight(node);
// Double pointer to create 2D array
int [,]mtrx = new int[width,height];
// Initialize complete matrix with
// MAX INTEGER(purpose garbage)
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
mtrx[i, j] = 100000000;
}
}
// Store the BFS traversal of the tree
// into the 2-D matrix
BFS(mtrx, node);
// Print the circular clockwise spiral
// traversal of the tree
traverse_matrix(mtrx, height, width);
// release extra memory
// allocated for matrix
mtrx = null;
}
// Driver Code
public static void Main(string[] args)
{
/*
10
/ \
12 13
/ \
14 15
/ \ / \
21 22 23 24
*/
// Creating the above tree
Node root = newNode(10);
root.left = newNode(12);
root.right = newNode(13);
root.right.left = newNode(14);
root.right.right = newNode(15);
root.right.left.left = newNode(21);
root.right.left.right = newNode(22);
root.right.right.left = newNode(23);
root.right.right.right = newNode(24);
printPattern(root);
}
}
// This code is contributed by rutvik_56输出：
14, 15,
12, 13,
21, 22, 23, 24,
10,