[Leetcode] 545. Boundary of Binary Tree 解题报告

魔豆Magicbean

于 2017-12-21 14:07:29 发布

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分类专栏： IT公司面试习题文章标签： Leetcode 解题报告 Tree

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本文详细介绍了LeetCode第545题《二叉树的边界遍历》的解题思路。题目要求按逆时针方向返回二叉树的边界节点，包括左边界、叶子节点和右边界。文章首先定义了左边界和右边界的概念，并给出两个示例。解题策略是先获取左边界，再分别收集左子树和右子树的叶子节点，最后计算右边界，并注意去重和避免重复添加根节点。

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题目：

Given a binary tree, return the values of its boundary in anti-clockwise direction starting from root. Boundary includes left boundary, leaves, and right boundary in order without duplicate nodes.

Left boundary is defined as the path from root to the left-most node. Right boundary is defined as the path from root to the right-most node. If the root doesn't have left subtree or right subtree, then the root itself is left boundary or right boundary. Note this definition only applies to the input binary tree, and not applies to any subtrees.

The left-most node is defined as a leaf node you could