872. Leaf-Similar Trees

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于 2019-03-09 18:14:58 发布

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本文介绍了一种算法，用于判断两棵二叉树是否具有相同的叶子节点序列。通过深度优先搜索遍历树结构，收集所有叶子节点的值，并比较两个序列是否相等来实现。适用于1到100个节点的二叉树。

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题目描述

Consider all the leaves of a binary tree. From left to right order, the values of those leaves form a leaf value sequence.
在这里插入图片描述
For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8).

Two binary trees are considered leaf-similar if their leaf value sequence is the same.

Return true if and only if the two given trees with head nodes root1 and root2 are leaf-similar.

Note:

Both of the given trees will have between 1 and 100 nodes.

方法思路

class Solution {
    //Runtime: 2 ms, faster than 95.33%
    //Memory Usage: 37.3 MB, less than 10.51%
    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
        List<Integer> leaves1 = new ArrayList();
        List<Integer> leaves2 = new ArrayList();
        dfs(root1, leaves1);
        dfs(root2, leaves2);
        return leaves1.equals(leaves2);
    }

    public void dfs(TreeNode node, List<Integer> leafValues) {
        if (node != null) {
            if (node.left == null && node.right == null)
                leafValues.add(node.val);
            dfs(node.left, leafValues);
            dfs(node.right, leafValues);
        }
    }
}