leetcode讲解--872. Leaf-Similar Trees

题目Consider all the leaves of a binary tree. From left to right order, the values of those leaves form a leaf value sequence.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.讲解这道题的思路很简单，先扫描出两个树的叶子结果集，然后比较就行了。考察点是树的遍历。递归的时候首先要判断结点是否为空。Java代码/** * 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> leaves1 = new ArrayList<>(); List<Integer> leaves2 = new ArrayList<>(); getLeaves(root1, leaves1); getLeaves(root2, leaves2); if(leaves1.size()!=leaves2.size()){ return false; }else{ for(int i=0;i<leaves1.size();i++){ if(leaves1.get(i)!=leaves2.get(i)){ return false; } } } return true; } private void getLeaves(TreeNode root, List<Integer> leaves){ if(root==null){ return; } if(root.left==null && root.right==null){ leaves.add(root.val); return; } getLeaves(root.left, leaves); getLeaves(root.right, leaves); }}