872. 叶子相似的树

Posted 2021-05-15 lgz0921

题目链接：https://leetcode-cn.com/problems/leaf-similar-trees/

思路：题目要求的叶子顺序，正好是每次从左子树开始递归得到叶子的顺序。递归两棵树，按照递归得到的顺序存下叶子节点（两个list），判断两个list是否相等即可。

kotlin知识点：a == b比较的是数值（相当于equals()，现在好的编译器（比如idea）写equals()，会提示改成==了），a === b比较的是地址

上代码：
 

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
   fun getLeaf(root: TreeNode, leafList: ArrayList<Int>) {
        if (root.left == null && root.right == null) {
            leafList.add(root.`val`)
            return
        }
        root.left?.let { x -> getLeaf(x, leafList) }
        root.right?.let { x -> getLeaf(x, leafList) }
    }

    fun leafSimilar(root1: TreeNode?, root2: TreeNode?): Boolean {
        val treeOne = ArrayList<Int>()
        val treeTwo = ArrayList<Int>()
        getLeaf(root1!!, treeOne)
        getLeaf(root2!!, treeTwo)
        return treeOne == treeTwo
    }
}