LeetCode 筆記 - 515. Find Largest Value in Each Tree Row

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題目在此 515. Find Largest Value in Each Tree Row

給定一棵 Binary Tree，請回傳每一層最大的數字

解題思維

可以使用 Breadth-First Search 一次走訪同一層的節點

紀錄看到最大數值即可

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 largestValues(self, root: Optional[TreeNode]) -> List[int]:
        
        if not root:
            return root
        
        upper_quque = [root]
        lower_quque = []
        
        result = []
        while upper_quque:
            
            current_max = -inf
            for node in upper_quque:
                if node.left:
                    lower_quque.append(node.left)
                if node.right:
                    lower_quque.append(node.right)
                current_max = max(current_max, node.val)
            
            if current_max != -inf:
                result.append(current_max)

            upper_quque = lower_quque
            lower_quque = []
        
        return result

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