feat: solve No.2265

BaffinLee · BaffinLee · commit 7bebc6f45b72 · 2023-11-02T15:28:28.000Z
diff --git a/2201-2300/2265. Count Nodes Equal to Average of Subtree.md b/2201-2300/2265. Count Nodes Equal to Average of Subtree.md
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+# 2265. Count Nodes Equal to Average of Subtree
+
+- Difficulty: Medium.
+- Related Topics: Tree, Depth-First Search, Binary Tree.
+- Similar Questions: Maximum Average Subtree, Insufficient Nodes in Root to Leaf Paths, Count Nodes Equal to Sum of Descendants.
+
+## Problem
+
+Given the `root` of a binary tree, return **the number of nodes where the value of the node is equal to the **average** of the values in its **subtree****.
+
+**Note:**
+
+
+	
+- The **average** of `n` elements is the **sum** of the `n` elements divided by `n` and **rounded down** to the nearest integer.
+	
+- A **subtree** of `root` is a tree consisting of `root` and all of its descendants.
+
+
+ 
+Example 1:
+
+![](https://assets.leetcode.com/uploads/2022/03/15/image-20220315203925-1.png)
+
+```
+Input: root = [4,8,5,0,1,null,6]
+Output: 5
+Explanation: 
+For the node with value 4: The average of its subtree is (4 + 8 + 5 + 0 + 1 + 6) / 6 = 24 / 6 = 4.
+For the node with value 5: The average of its subtree is (5 + 6) / 2 = 11 / 2 = 5.
+For the node with value 0: The average of its subtree is 0 / 1 = 0.
+For the node with value 1: The average of its subtree is 1 / 1 = 1.
+For the node with value 6: The average of its subtree is 6 / 1 = 6.
+```
+
+Example 2:
+
+![](https://assets.leetcode.com/uploads/2022/03/26/image-20220326133920-1.png)
+
+```
+Input: root = [1]
+Output: 1
+Explanation: For the node with value 1: The average of its subtree is 1 / 1 = 1.
+```
+
+ 
+**Constraints:**
+
+
+	
+- The number of nodes in the tree is in the range `[1, 1000]`.
+	
+- `0 <= Node.val <= 1000`
+
+
+
+## Solution
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var averageOfSubtree = function(root) {
+    return helper(root).res;
+};
+
+var helper = function(root) {
+    if (!root) return { sum: 0, num: 0, res: 0 };
+    var left = helper(root.left);
+    var right = helper(root.right);
+    var sum = left.sum + right.sum + root.val;
+    var num = left.num + right.num + 1;
+    var res = left.res + right.res + (Math.floor(sum / num) === root.val ? 1 : 0);
+    return { sum, num, res };
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).
