按排序顺序打印二叉树级别 |第 3 组（以数组形式给出的树）

给定一个完整的二叉树作为一个数组，任务是按排序顺序打印它的所有级别。
例子：

Input: arr[] = {7, 6, 5, 4, 3, 2, 1}
The given tree looks like
            7
          /   \
        6      5
       / \    / \
      4  3   2   1
Output:
7
5 6
1 2 3 4

Input: arr[] = {5, 6, 4, 9, 2, 1}
The given tree looks like 
            5
          /   \
        6      4
       / \    /    
      9   2  1
Output: 
5
4 6
1 2 9

方法：这里讨论了一个类似的问题
由于给定的树是完全二叉树：

No. of nodes at a level l will be 2l where l ≥ 0

1. 开始遍历数组，级别初始化为 0。
2. 对属于当前关卡的元素进行排序并打印这些元素。

下面是上述方法的实现：

C++

// C++ implementation of the approach
#include 
using namespace std;
 
// Function to print all the levels
// of the given tree in sorted order
void printSortedLevels(int arr[], int n)
{
 
    // Initialize level with 0
    int level = 0;
    for (int i = 0; i < n; level++) {
 
        // Number of nodes at current level
        int cnt = (int)pow(2, level);
 
        // Indexing of array starts from 0
        // so subtract no. of nodes by 1
        cnt -= 1;
 
        // Index of the last node in the current level
        int j = min(i + cnt, n - 1);
 
        // Sort the nodes of the current level
        sort(arr + i, arr + j + 1);
 
        // Print the sorted nodes
        while (i <= j) {
            cout << arr[i] << " ";
            i++;
        }
        cout << endl;
    }
}
 
// Driver code
int main()
{
    int arr[] = { 5, 6, 4, 9, 2, 1 };
    int n = sizeof(arr) / sizeof(arr[0]);
    printSortedLevels(arr, n);
 
    return 0;
}

Java

// Java implementation of the approach
import java.util.Arrays;
 
class GFG
{
 
// Function to print all the levels
// of the given tree in sorted order
static void printSortedLevels(int arr[], int n)
{
 
    // Initialize level with 0
    int level = 0;
    for (int i = 0; i < n; level++)
    {
 
        // Number of nodes at current level
        int cnt = (int)Math.pow(2, level);
 
        // Indexing of array starts from 0
        // so subtract no. of nodes by 1
        cnt -= 1;
 
        // Index of the last node in the current level
        int j = Math.min(i + cnt, n - 1);
 
        // Sort the nodes of the current level
        Arrays.sort(arr, i, j+1);
 
        // Print the sorted nodes
        while (i <= j)
        {
            System.out.print(arr[i] + " ");
            i++;
        }
        System.out.println();
    }
}
 
// Driver code
public static void main(String[] args)
{
    int arr[] = { 5, 6, 4, 9, 2, 1 };
    int n = arr.length;
    printSortedLevels(arr, n);
}
}
 
// This code is contributed by 29AjayKumar

Python3

# Python3 implementation of the approach
from math import pow
 
# Function to print all the levels
# of the given tree in sorted order
def printSortedLevels(arr, n):
     
    # Initialize level with 0
    level = 0
    i = 0
    while(i < n):
         
        # Number of nodes at current level
        cnt = int(pow(2, level))
 
        # Indexing of array starts from 0
        # so subtract no. of nodes by 1
        cnt -= 1
 
        # Index of the last node in the current level
        j = min(i + cnt, n - 1)
         
        # Sort the nodes of the current level
        arr = arr[:i] + sorted(arr[i:j + 1]) + \
                               arr[j + 1:]
 
        # Print the sorted nodes
        while (i <= j):
            print(arr[i], end = " ")
            i += 1
        print()
        level += 1
 
# Driver code
arr = [ 5, 6, 4, 9, 2, 1]
n = len(arr)
printSortedLevels(arr, n)
 
# This code is contributed by SHUBHAMSINGH10

C#

// C# implementation of the approach
using System;
using System.Linq;                
     
class GFG
{
 
// Function to print all the levels
// of the given tree in sorted order
static void printSortedLevels(int []arr, int n)
{
 
    // Initialize level with 0
    int level = 0;
    for (int i = 0; i < n; level++)
    {
 
        // Number of nodes at current level
        int cnt = (int)Math.Pow(2, level);
 
        // Indexing of array starts from 0
        // so subtract no. of nodes by 1
        cnt -= 1;
 
        // Index of the last node in the current level
        int j = Math.Min(i + cnt, n - 1);
 
        // Sort the nodes of the current level
        Array.Sort(arr, i, j + 1 - i);
 
        // Print the sorted nodes
        while (i <= j)
        {
            Console.Write(arr[i] + " ");
            i++;
        }
        Console.WriteLine();
    }
}
 
// Driver code
public static void Main(String[] args)
{
    int []arr = { 5, 6, 4, 9, 2, 1 };
    int n = arr.Length;
    printSortedLevels(arr, n);
}
}
 
// This code is contributed by 29AjayKumar

Javascript

 
    // JavaScript implementation of the approach
     
    // Function to sort the elements of the array
    // from index a to index b
    function partSort(arr, N, a, b)
    {
        // Variables to store start and end of the index range
        let l = Math.min(a, b);
        let r = Math.max(a, b);
   
        // Temporary array
        let temp = new Array(r - l + 1);
        temp.fill(0);
        let j = 0;
        for (let i = l; i <= r; i++) {
            temp[j] = arr[i];
            j++;
        }
   
        // Sort the temporary array
        temp.sort(function(a, b){return a - b});
   
        // Modifying original array with temporary array elements
        j = 0;
        for (let i = l; i <= r; i++) {
            arr[i] = temp[j];
            j++;
        }
    }
     
    // Function to print all the levels
    // of the given tree in sorted order
    function printSortedLevels(arr, n)
    {
 
        // Initialize level with 0
        let level = 0;
        for (let i = 0; i < n; level++)
        {
 
            // Number of nodes at current level
            let cnt = Math.pow(2, level);
 
            // Indexing of array starts from 0
            // so subtract no. of nodes by 1
            cnt -= 1;
 
            // Index of the last node in the current level
            let j = Math.min(i + cnt, n - 1);
 
            // Sort the nodes of the current level
            partSort(arr, n, i, j + 1);
 
            // Print the sorted nodes
            while (i <= j)
            {
                document.write(arr[i] + " ");
                i++;
            }
            document.write("</br>");
        }
    }
     
    let arr = [ 5, 6, 4, 9, 2, 1 ];
    let n = arr.length;
    printSortedLevels(arr, n);
     

输出：

5 
4 6 
1 2 9