给定一棵树，按排序顺序打印级别顺序遍历。
例子 ：
Input : 7
/ \
6 5
/ \ / \
4 3 2 1
Output :
7
5 6
1 2 3 4
Input : 7
/ \
16 1
/ \
4 13
Output :
7
1 16
4 13
我们在下面的文章中讨论了基于优先级队列的解决方案。
按排序顺序打印二叉树级别|设置1(使用优先级队列)
在这篇文章中，讨论了一个基于集合(使用平衡二叉搜索树实现)的解决方案。
方法 ：
1.开始遍历树。
2.将所有节点存储在一个集合(或任何其他类似的数据结构)中。
3.打印集合的元素。
C++
// CPP code to print level order
// traversal in sorted order
#include
using namespace std;
struct Node {
int data;
Node* left;
Node* right;
Node(int dat = 0)
: data(dat), left(nullptr),
right(nullptr)
{
}
};
// Function to print sorted
// level order traversal
void sorted_level_order(Node* root)
{
queue q;
set s;
q.push(root);
q.push(nullptr);
while (q.empty() == false) {
Node* tmp = q.front();
q.pop();
if (tmp == nullptr) {
if (s.empty() == true)
break;
for (set::iterator it =
s.begin();it != s.end(); ++it)
cout << *it << " ";
q.push(nullptr);
s.clear();
}
else {
s.insert(tmp->data);
if (tmp->left != nullptr)
q.push(tmp->left);
if (tmp->right != nullptr)
q.push(tmp->right);
}
}
}
// Driver code
int main()
{
Node* root = new Node(7);
root->left = new Node(6);
root->right = new Node(5);
root->left->left = new Node(4);
root->left->right = new Node(3);
root->right->left = new Node(2);
root->right->right = new Node(1);
sorted_level_order(root);
return 0;
} Java
// Java code to print level order
// traversal in sorted order
import java.util.*;
import java.util.HashSet;
class GFG
{
static class Node
{
int data;
Node left, right;
};
static Node newNode(int data)
{
Node node = new Node();
node.data = data;
node.left = node.right = null;
return (node);
}
// Function to print sorted
// level order traversal
static void sorted_level_order(Node root)
{
Queue q = new LinkedList<>();
Set s = new HashSet();
q.add(root);
q.add(null);
while (!q.isEmpty())
{
Node tmp = q.peek();
q.remove();
if (tmp == null)
{
if (s.isEmpty())
break;
Iterator value = s.iterator();
while (value.hasNext())
{
System.out.print(value.next() + " ");
}
q.add(null);
s.clear();
}
else
{
s.add(tmp.data);
if (tmp.left != null)
q.add(tmp.left);
if (tmp.right != null)
q.add(tmp.right);
}
}
}
// Driver Code
public static void main(String[] args)
{
Node root = newNode(7);
root.left = newNode(6);
root.right = newNode(5);
root.left.left = newNode(4);
root.left.right = newNode(3);
root.right.left = newNode(2);
root.right.right = newNode(1);
sorted_level_order(root);
}
}
// This code is contributed by SHUBHAMSINGH10 Python3
# Python3 program to print level order
# traversal in sorted order
# Helper function that allocates a new
# node with the given data and None
# left and right poers.
class newNode:
# Construct to create a new node
def __init__(self, key):
self.data = key
self.left = None
self.right = None
# Function to print sorted
# level order traversal
def sorted_level_order( root):
q = []
s = set()
q.append(root)
q.append(None)
while (len(q)):
tmp = q[0]
q.pop(0)
if (tmp == None):
if (not len(s)):
break
for i in s:
print(i, end = " ")
q.append(None)
s = set()
else :
s.add(tmp.data)
if (tmp.left != None):
q.append(tmp.left)
if (tmp.right != None):
q.append(tmp.right)
# Driver Code
if __name__ == '__main__':
"""
Let us create Binary Tree shown
in above example """
root = newNode(7)
root.left = newNode(6)
root.right = newNode(5)
root.left.left = newNode(4)
root.left.right = newNode(3)
root.right.left = newNode(2)
root.right.right = newNode(1)
sorted_level_order(root)
# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)C#
// C# code to print level order
// traversal in sorted order
using System;
using System.Collections.Generic;
class GFG
{
public class Node
{
public int data;
public Node left, right;
};
static Node newNode(int data)
{
Node node = new Node();
node.data = data;
node.left = node.right = null;
return (node);
}
// Function to print sorted
// level order traversal
static void sorted_level_order(Node root)
{
Queue q = new Queue();
SortedSet s = new SortedSet();
q.Enqueue(root);
q.Enqueue(null);
while (q.Count != 0)
{
Node tmp = q.Peek();
q.Dequeue();
if (tmp == null)
{
if (s.Count == 0)
break;
foreach (int v in s)
{
Console.Write(v + " ");
}
q.Enqueue(null);
s.Clear();
}
else
{
s.Add(tmp.data);
if (tmp.left != null)
q.Enqueue(tmp.left);
if (tmp.right != null)
q.Enqueue(tmp.right);
}
}
}
// Driver Code
public static void Main(String[] args)
{
Node root = newNode(7);
root.left = newNode(6);
root.right = newNode(5);
root.left.left = newNode(4);
root.left.right = newNode(3);
root.right.left = newNode(2);
root.right.right = newNode(1);
sorted_level_order(root);
}
}
// This code is contributed by 29AjayKumar 输出：
7 5 6 1 2 3 4