给定一个二叉树和一个整数K ，其中树有正节点和负节点，任务是打印总和等于K的级别的元素。如果不存在这样的结果，则打印“不可能”。
例子：
Input:
-10
/ \
2 -3
/ \ \
4 15 -6
/ \ /
7 -8 9
K = 13
Output: 4 15 -6
Explanation:
Level 1 (-10): Sum = -10
Level 2 (2, 3): Sum = 5
Level 3 (4, 15, -6): Sum = 13
Level 4 (7, -8, 9): Sum = 8
Only level 3 (4, 15, -6) has sum = K
Input:
1
/ \
12 13
/ / \
11 6 -11
\ /
2 2
K = 30
Output: Not Possible
Explanation:
There is no such level whose sum = K方法：
- 执行二叉树的级别顺序遍历并存储找到每个级别的总和。
- 如果总和等于 K，则打印级别。否则进入下一个级别。
- 重复该过程，直到遍历并检查了所有级别。
- 如果总和 K 不存在这样的级别，则打印“不可能”。
下面是上述方法的实现：
C++
// C++ program to print all
// K-sum levels in a Binary Tree
#include
using namespace std;
// Vector to store the
// elements of a level
vector level;
// Binary Tree Node
struct node {
struct node* left;
int data;
struct node* right;
};
// Function to display elements
void display(bool flag)
{
// Check if boolean variable is true
// then print the level
if (flag) {
for (auto x : level)
cout << x << " ";
}
else
cout << "Not Possible\n";
}
// Function to find sum of
// elements by level order traversal
void SumlevelOrder(node* root, int k)
{
if (root == NULL)
return;
// Queue data structure for
// level order traversal
queue q;
// Enqueue Root in Queue
q.push(root);
bool flag = false;
while (q.empty() == false) {
// number of nodes at current level
int nodeCount = q.size();
int Present_level_sum = 0;
// Dequeue all nodes of current level and
// Enqueue all nodes of next level
while (nodeCount > 0) {
node* node = q.front();
// To add node data
Present_level_sum += node->data;
level.push_back(node->data);
q.pop();
if (node->left != NULL)
q.push(node->left);
if (node->right != NULL)
q.push(node->right);
nodeCount--;
}
if (Present_level_sum == k) {
flag = true;
break;
}
level.clear();
}
display(flag);
}
// Function to create a new tree node
node* newNode(int data)
{
node* temp = new node;
temp->data = data;
temp->left = NULL;
temp->right = NULL;
return temp;
}
// Driver code
int main()
{
// Create binary tree
node* root = newNode(1);
root->left = newNode(2);
root->right = newNode(3);
root->left->left = newNode(4);
root->left->right = newNode(5);
root->right->right = newNode(6);
int K = 15;
SumlevelOrder(root, K);
return 0;
} Java
// Java program to print all
// K-sum levels in a Binary Tree
import java.util.*;
class GFG{
// Vector to store the
// elements of a level
static Vector level = new Vector();
// Binary Tree Node
static class node {
node left;
int data;
node right;
};
// Function to display elements
static void display(boolean flag)
{
// Check if boolean variable is true
// then print the level
if (flag) {
for (Integer x : level)
System.out.print(x+ " ");
}
else
System.out.print("Not Possible\n");
}
// Function to find sum of
// elements by level order traversal
static void SumlevelOrder(node root, int k)
{
if (root == null)
return;
// Queue data structure for
// level order traversal
Queue q = new LinkedList<>();
// Enqueue Root in Queue
q.add(root);
boolean flag = false;
while (q.isEmpty() == false) {
// number of nodes at current level
int nodeCount = q.size();
int Present_level_sum = 0;
// Dequeue all nodes of current level and
// Enqueue all nodes of next level
while (nodeCount > 0) {
node node = q.peek();
// To add node data
Present_level_sum += node.data;
level.add(node.data);
q.remove();
if (node.left != null)
q.add(node.left);
if (node.right != null)
q.add(node.right);
nodeCount--;
}
if (Present_level_sum == k) {
flag = true;
break;
}
level.clear();
}
display(flag);
}
// Function to create a new tree node
static node newNode(int data)
{
node temp = new node();
temp.data = data;
temp.left = null;
temp.right = null;
return temp;
}
// Driver code
public static void main(String[] args)
{
// Create binary tree
node root = newNode(1);
root.left = newNode(2);
root.right = newNode(3);
root.left.left = newNode(4);
root.left.right = newNode(5);
root.right.right = newNode(6);
int K = 15;
SumlevelOrder(root, K);
}
}
// This code is contributed by 29AjayKumar Python3
# Python3 program to prall
# K-sum levels in a Binary Tree
from collections import deque as queue
# A BST node
class Node:
def __init__(self, x):
self.data = x
self.left = None
self.right = None
# Vector to store the
# elements of a level
level = []
# Function to display elements
def display(flag):
# Check if boolean variable is
# true then print level
if (flag):
for x in level:
print(x, end = " ")
else:
print("Not Possible\n")
# Function to find sum of elements
# by level order traversal
def SumlevelOrder(root, k):
if (root == None):
return
# Queue data structure for
# level order traversal
q = queue()
# Enqueue Root in Queue
q.append(root)
flag = False
while (len(q) > 0):
# Number of nodes at current level
nodeCount = len(q)
Present_level_sum = 0
# Dequeue all nodes of current level
# and Enqueue all nodes of next level
while (nodeCount > 0):
node = q.popleft()
# To add node data
Present_level_sum += node.data
level.append(node.data)
# q.pop()
if (node.left != None):
q.append(node.left)
if (node.right != None):
q.append(node.right)
nodeCount -= 1
if (Present_level_sum == k):
flag = True
break
level.clear()
display(flag)
# Driver code
if __name__ == '__main__':
# Create binary tree
root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.right = Node(6)
K = 15
SumlevelOrder(root, K)
# This code is contributed by mohit kumar 29C#
// C# program to print all
// K-sum levels in a Binary Tree
using System;
using System.Collections.Generic;
class GFG{
// List to store the
// elements of a level
static List level = new List();
// Binary Tree Node
class node {
public node left;
public int data;
public node right;
};
// Function to display elements
static void display(bool flag)
{
// Check if bool variable is true
// then print the level
if (flag) {
foreach (int x in level)
Console.Write(x+ " ");
}
else
Console.Write("Not Possible\n");
}
// Function to find sum of
// elements by level order traversal
static void SumlevelOrder(node root, int k)
{
if (root == null)
return;
// Queue data structure for
// level order traversal
Queue q = new Queue();
// Enqueue Root in Queue
q.Enqueue(root);
bool flag = false;
while (q.Count!=0) {
// number of nodes at current level
int nodeCount = q.Count;
int Present_level_sum = 0;
// Dequeue all nodes of current level and
// Enqueue all nodes of next level
while (nodeCount > 0) {
node node = q.Peek();
// To add node data
Present_level_sum += node.data;
level.Add(node.data);
q.Dequeue();
if (node.left != null)
q.Enqueue(node.left);
if (node.right != null)
q.Enqueue(node.right);
nodeCount--;
}
if (Present_level_sum == k) {
flag = true;
break;
}
level.Clear();
}
display(flag);
}
// Function to create a new tree node
static node newNode(int data)
{
node temp = new node();
temp.data = data;
temp.left = null;
temp.right = null;
return temp;
}
// Driver code
public static void Main(String[] args)
{
// Create binary tree
node root = newNode(1);
root.left = newNode(2);
root.right = newNode(3);
root.left.left = newNode(4);
root.left.right = newNode(5);
root.right.right = newNode(6);
int K = 15;
SumlevelOrder(root, K);
}
}
// This code is contributed by sapnasingh4991 输出：
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