打印二叉树顶视图中的节点 |设置 2
二叉树的顶视图是从顶部查看树时可见的节点集。给定一棵二叉树，打印它的顶视图。输出节点应该从左到右打印。
注意：如果 x 是其水平距离处的最顶部节点，则输出中存在节点 x。节点x的左孩子的水平距离等于x的水平距离减1，右孩子的水平距离是x的水平距离加1。
Input:
1
/ \
2 3
/ \ / \
4 5 6 7
Output: Top view: 4 2 1 3 7
Input:
1
/ \
2 3
\
4
\
5
\
6
Output: Top view: 2 1 3 6这个想法是做一些类似于垂直顺序遍历的事情。像垂直顺序遍历一样，我们需要将相同水平距离的节点组合在一起。我们进行水平顺序遍历，以便水平节点的最顶端节点在其下方具有相同水平距离的任何其他节点之前被访问。 Map用于将节点的水平距离与节点的Data和节点的垂直距离进行映射。
下面是上述方法的实现：
C++
// C++ Program to print Top View of Binary Tree
// using hashmap and recursion
#include
using namespace std;
// Node structure
struct Node {
// Data of the node
int data;
// Horizontal Distance of the node
int hd;
// Reference to left node
struct Node* left;
// Reference to right node
struct Node* right;
};
// Initialising node
struct Node* newNode(int data)
{
struct Node* node = new Node;
node->data = data;
node->hd = INT_MAX;
node->left = NULL;
node->right = NULL;
return node;
}
void printTopViewUtil(Node* root, int height,
int hd, map >& m)
{
// Base Case
if (root == NULL)
return;
// If the node for particular horizontal distance
// is not present in the map, add it.
// For top view, we consider the first element
// at horizontal distance in level order traversal
if (m.find(hd) == m.end()) {
m[hd] = make_pair(root->data, height);
}
else{
pair p = (m.find(hd))->second;
if (p.second > height) {
m.erase(hd);
m[hd] = make_pair(root->data, height);
}
}
// Recur for left and right subtree
printTopViewUtil(root->left, height + 1, hd - 1, m);
printTopViewUtil(root->right, height + 1, hd + 1, m);
}
void printTopView(Node* root)
{
// Map to store horizontal distance,
// height and node's data
map > m;
printTopViewUtil(root, 0, 0, m);
// Print the node's value stored by printTopViewUtil()
for (map >::iterator it = m.begin();
it != m.end(); it++) {
pair p = it->second;
cout << p.first << " ";
}
}
int main()
{
Node* root = newNode(1);
root->left = newNode(2);
root->right = newNode(3);
root->left->right = newNode(4);
root->left->right->right = newNode(5);
root->left->right->right->right = newNode(6);
cout << "Top View : ";
printTopView(root);
return 0;
} Java
// Java Program to print Top View of Binary Tree
// using hashmap and recursion
import java.util.*;
class GFG {
// Node structure
static class Node {
// Data of the node
int data;
// Reference to left node
Node left;
// Reference to right node
Node right;
};
static class pair {
int data, height;
public pair(int data, int height)
{
this.data = data;
this.height = height;
}
}
// Initialising node
static Node newNode(int data)
{
Node node = new Node();
node.data = data;
node.left = null;
node.right = null;
return node;
}
static void printTopViewUtil(Node root, int height,
int hd,
Map m)
{
// Base Case
if (root == null)
return;
// If the node for particular horizontal distance
// is not present in the map, add it.
// For top view, we consider the first element
// at horizontal distance in level order traversal
if (!m.containsKey(hd)) {
m.put(hd, new pair(root.data, height));
}
else {
pair p = m.get(hd);
if (p.height >= height) {
m.put(hd, new pair(root.data, height));
}
}
// Recur for left and right subtree
printTopViewUtil(root.left, height + 1, hd - 1, m);
printTopViewUtil(root.right, height + 1, hd + 1, m);
}
static void printTopView(Node root)
{
// Map to store horizontal distance,
// height and node's data
Map m = new TreeMap<>();
printTopViewUtil(root, 0, 0, m);
// Print the node's value stored by
// printTopViewUtil()
for (Map.Entry it : m.entrySet()) {
pair p = it.getValue();
System.out.print(p.data + " ");
}
}
// Driver code
public static void main(String[] args)
{
Node root = newNode(1);
root.left = newNode(2);
root.right = newNode(3);
root.left.right = newNode(4);
root.left.right.right = newNode(5);
root.left.right.right.right = newNode(6);
System.out.print("Top View : ");
printTopView(root);
}
} Python3
# Python3 Program to prTop View of
# Binary Tree using hash and recursion
from collections import OrderedDict
# A binary tree node
class newNode:
# A constructor to create a
# new Binary tree Node
def __init__(self, data):
self.data = data
self.left = None
self.right = None
self.hd = 2**32
def printTopViewUtil(root, height, hd, m):
# Base Case
if (root == None):
return
# If the node for particular horizontal
# distance is not present in the map, add it.
# For top view, we consider the first element
# at horizontal distance in level order traversal
if hd not in m :
m[hd] = [root.data, height]
else:
p = m[hd]
if p[1] > height:
m[hd] = [root.data, height]
# Recur for left and right subtree
printTopViewUtil(root.left,
height + 1, hd - 1, m)
printTopViewUtil(root.right,
height + 1, hd + 1, m)
def printTopView(root):
# to store horizontal distance,
# height and node's data
m = OrderedDict()
printTopViewUtil(root, 0, 0, m)
# Print the node's value stored
# by printTopViewUtil()
for i in sorted(list(m)):
p = m[i]
print(p[0], end = " ")
# Driver Code
root = newNode(1)
root.left = newNode(2)
root.right = newNode(3)
root.left.right = newNode(4)
root.left.right.right = newNode(5)
root.left.right.right.right = newNode(6)
print("Top View : ", end = "")
printTopView(root)
# This code is contributed by SHUBHAMSINGH10C#
// C# program to print Top View of Binary
// Tree using hashmap and recursion
using System;
using System.Collections.Generic;
class GFG{
// Node structure
class Node
{
// Data of the node
public int data;
// Reference to left node
public Node left;
// Reference to right node
public Node right;
};
class pair
{
public int data, height;
public pair(int data, int height)
{
this.data = data;
this.height = height;
}
}
// Initialising node
static Node newNode(int data)
{
Node node = new Node();
node.data = data;
node.left = null;
node.right = null;
return node;
}
static void printTopViewUtil(Node root, int height,
int hd,
SortedDictionary m)
{
// Base Case
if (root == null)
return;
// If the node for particular horizontal distance
// is not present in the map, add it.
// For top view, we consider the first element
// at horizontal distance in level order traversal
if (!m.ContainsKey(hd))
{
m[hd] = new pair(root.data, height);
}
else
{
pair p = m[hd];
if (p.height >= height)
{
m[hd] = new pair(root.data, height);
}
}
// Recur for left and right subtree
printTopViewUtil(root.left, height + 1,
hd - 1, m);
printTopViewUtil(root.right, height + 1,
hd + 1, m);
}
static void printTopView(Node root)
{
// Map to store horizontal distance,
// height and node's data
SortedDictionary m = new SortedDictionary();
printTopViewUtil(root, 0, 0, m);
// Print the node's value stored by
// printTopViewUtil()
foreach(var it in m.Values)
{
Console.Write(it.data + " ");
}
}
// Driver code
public static void Main(string[] args)
{
Node root = newNode(1);
root.left = newNode(2);
root.right = newNode(3);
root.left.right = newNode(4);
root.left.right.right = newNode(5);
root.left.right.right.right = newNode(6);
Console.Write("Top View : ");
printTopView(root);
}
}
// This code is contributed by rutvik_56 Javascript
输出
Top View : 2 1 3 6