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674. Longest Continuous Increasing Subsequence

leetcode easy-problem binary-search tree

URL: LeetCode Problem

Problem Description

Given the root of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within 10-5 of the actual answer will be accepted.

Examples:

  • Example 1: tree
    Input: root = [3,9,20,null,null,15,7]
Output: [3.00000,14.50000,11.00000]
Explanation: The average value of nodes on level 0 is 3, on level 1 is 14.5, and on level 2 is 11.
Hence return [3, 14.5, 11].

Constraints:

The number of nodes in the tree is in the range [1, 104]. -231 <= Node.val <= 231 - 1

Python3 Solution 

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def averageOfLevels(self, root: Optional[TreeNode]) -> List[float]:
        ans = []
        # nodes store
        q = deque()
        q.append(root)

        while q:
            # list of node values on same levels
            level = []
            for _ in range(len(q)):
                popping = q.popleft()
                if popping:
                    level.append(popping.val)
                    q.append(popping.left)
                    q.append(popping.right)
            if level:
                ans.append(level)
        return [sum(nums)/len(nums) for nums in ans]