LeetCode 筆記 - 1302. Deepest Leaves Sum

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題目在此 1302. Deepest Leaves Sum

給定一個 Binary Tree，計算出最深 node 的總和

image 10

解題思維

這題的關鍵就是找出同一層的 node 有哪些
在這裡 Breadth-First Search 剛好可以幫上我們的忙

透過搜索的順序，最終我們就可以知道 最底層的 node 有哪些

程式碼

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# 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 deepestLeavesSum(self, root: Optional[TreeNode]) -> int:
        if not root:
            return root
        
        upper_quque = [root]
        lower_quque = []
        
        result = 0
        while upper_quque:           
            for node in upper_quque:
                if node.left:
                    lower_quque.append(node.left)
                if node.right:
                    lower_quque.append(node.right)
            if not lower_quque:
                for node in upper_quque:
                    result += node.val
                break
            upper_quque = lower_quque
            lower_quque = []
        
        return result

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