给定一棵二叉树，任务是计算给定树中平衡节点的数量。
Balanced nodes of a binary tree are defined as the nodes which contains both left and right subtrees with their respective sum of node values equal.
例子：
Input:
Output: 1
Explanation:
Only node 9 contains the left subtree sum = right subtree sum = 4
Therefore, the required output is 1.
Input:
Output: 3
方法：这个想法是递归遍历给定二叉树的每个节点。对于每个节点，计算左右子树中节点的总和，并检查计算的总和是否相等。如果发现是真的，增加计数。最后，在完全遍历树后打印计数
请按照以下步骤解决问题：
- 初始化一个变量res来存储平衡节点的数量
- 递归计算每个节点的左右子树之和。
- 检查计算的总和是否相等。
- 如果发现为真，则当前节点是平衡的。因此，将res增加1
- 最后，在完全遍历树后打印res的值。
下面是上述方法的实现：
C++
9
/ \
2 4
/ \ \
-1 3 0
Java
7
/ \
4 10
/ \
3 3
/ \ \
0 0 -3
/
3
Python3
// C++ program to implement
// the above approach
#include
using namespace std;
// Structure of a
// Tree Node
struct Node {
int data;
Node* left;
Node* right;
Node(int val)
{
data = val;
left = right = NULL;
}
};
// Function to get the sum of left
// subtree and right subtree
int Sum(Node* root, int& res)
{
// Base case
if (root == NULL) {
return 0;
}
// Store the sum of
// left subtree
int leftSubSum
= Sum(root->left, res);
// Store the sum of
// right subtree
int rightSubSum
= Sum(root->right, res);
// Check if node is balanced or not
if (root->left and root->right
&& leftSubSum == rightSubSum)
// Increase count of
// balanced nodes
res += 1;
// Return subtree sum
return root->data + leftSubSum
+ rightSubSum;
}
// Driver Code
int main()
{
/*
9
/ \
2 4
/ \ \
-1 3 0
*/
// Insert nodes in tree
Node* root = new Node(9);
root->left = new Node(2);
root->left->left = new Node(-1);
root->left->right = new Node(3);
root->right = new Node(4);
root->right->right = new Node(0);
// Store the count of balanced nodes
int res = 0;
Sum(root, res);
cout << res;
} C#
// Java program to implement
// the above approach
class GFG{
static int res = 0;
// Structure of a
// Tree Node
static class Node
{
int data;
Node left;
Node right;
Node(int val)
{
data = val;
left = right = null;
}
};
// Function to get the sum of left
// subtree and right subtree
static int Sum(Node root)
{
// Base case
if (root == null)
{
return 0;
}
// Store the sum of
// left subtree
int leftSubSum = Sum(root.left);
// Store the sum of
// right subtree
int rightSubSum = Sum(root.right);
// Check if node is balanced or not
if (root.left != null && root.right != null &&
leftSubSum == rightSubSum)
// Increase count of
// balanced nodes
res += 1;
// Return subtree sum
return root.data + leftSubSum +
rightSubSum;
}
// Driver Code
public static void main(String[] args)
{
/*
9
/ \
2 4
/ \ \
-1 3 0
*/
// Insert nodes in tree
Node root = new Node(9);
root.left = new Node(2);
root.left.left = new Node(-1);
root.left.right = new Node(3);
root.right = new Node(4);
root.right.right = new Node(0);
// Store the count of balanced nodes
res = 0;
Sum(root);
System.out.print(res);
}
}
// This code is contributed by 29AjayKumar输出：
# Python3 program to implement
# the above approach
# Structure of a Tree Node
class Node:
def __init__(self, val):
self.data = val
self.left = None
self.right = None
# Function to get the sum of left
# subtree and right subtree
def Sum(root):
global res
# Base case
if (root == None):
return 0
# Store the sum of
# left subtree
leftSubSum = Sum(root.left)
# Store the sum of
# right subtree
rightSubSum = Sum(root.right)
# Check if node is balanced or not
if (root.left and root.right and
leftSubSum == rightSubSum):
# Increase count of
# balanced nodes
res += 1
# Return subtree sum
return (root.data + leftSubSum +
rightSubSum)
# Driver Code
"""
9
/ \
2 4
/ \ \
-1 3 0
"""
# Insert nodes in tree
root = Node(9)
root.left = Node(2)
root.left.left = Node(-1)
root.left.right = Node(3)
root.right = Node(4)
root.right.right = Node(0)
# Store the count of balanced nodes
global res
res = 0
Sum(root)
print(res)
# This code is contributed by Shivam Singh时间复杂度： O(N)
辅助空间： O(N)
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