LeetCode222. Count Complete Tree Nodes (思路及python解法)

Given a complete binary tree, count the number of nodes.

Note:

Definition of a complete binary tree from Wikipedia:
In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

Example:

Input: 
    1
   / \
  2   3
 / \  /
4  5 6

Output: 6

有很多种方法,直接用bfs算法统计每层个数即可。

class Solution:
    def countNodes(self, root: TreeNode) -> int:
        if root is None:return 0
        bfs=[root]
        sums=0
        while bfs:
            sums+=len(bfs)
            temp=[]
            for node in bfs:
                if node.left:
                    temp.append(node.left)
                if node.right:
                    temp.append(node.right)
            bfs=temp
        return sums

 

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