[leetcode] 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.

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> l1 = new ArrayList<>();
        List<Integer> l2 = new ArrayList<>();
        getLeaves(l1, root1);
        getLeaves(l2, root2);
        
        return l1.equals(l2);
    }
    
    public void getLeaves(List<Integer> l, TreeNode root){
        if(root == null) return;
        else if(root.left == null && root.right == null) l.add(root.val);
        else{
            getLeaves(l, root.left);
            getLeaves(l, root.right);
        }
    }
}