给定一个二叉树,返回它的 后序 遍历。
示例:
输入: [1,null,2,3]
输出: [3,2,1]
来源:力扣(LeetCode)
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 List<Integer> postorderTraversal(TreeNode root) {
List<Integer> result = new ArrayList<>();
if(root==null) {
return result;
}
result.addAll(postorderTraversal(root.left));
result.addAll(postorderTraversal(root.right));
result.add(root.val);
return result;
}
}
运行结果: