leetcode-872-Leaf-Similar-Trees

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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.

img

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.

分析

先序，中序，后序遍历都可以。

解决方案1(Java)

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
        List<Integer> list1 = new ArrayList<>();
        List<Integer> list2 = new ArrayList<>();
        
        preOrder(root1, list1);
        preOrder(root2, list2);
        return list1.equals(list2);
    }
    
    public void preOrder(TreeNode node, List list) {
        if (node == null) {
            return;
        }
        
        if (node.left == null && node.right == null) {
            list.add(node.val);
        }
        preOrder(node.left, list);
        preOrder(node.right, list);
    }
}

题目来源