網(wǎng)站建設(shè)沒業(yè)務(wù)互聯(lián)網(wǎng)產(chǎn)品推廣
給你一棵二叉樹的根節(jié)點(diǎn)?root
?,返回其節(jié)點(diǎn)值的?后序遍歷?。
示例 1:
輸入:root = [1,null,2,3]
輸出:[3,2,1]
解釋:
示例 2:
輸入:root = [1,2,3,4,5,null,8,null,null,6,7,9]
輸出:[4,6,7,5,2,9,8,3,1]
解釋:
示例 3:
輸入:root = []
輸出:[]
示例 4:
輸入:root = [1]
輸出:[1]
提示:
- 樹中節(jié)點(diǎn)的數(shù)目在范圍?
[0, 100]
?內(nèi) -100 <= Node.val <= 100
進(jìn)階:遞歸算法很簡單,你可以通過迭代算法完成嗎?
/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val = val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val = val;* this.left = left;* this.right = right;* }* }*/
class Solution {public List<Integer> postorderTraversal(TreeNode root) {List<Integer> list = new ArrayList<>();if (root != null) {list.addAll(postorderTraversal(root.left));list.addAll(postorderTraversal(root.right));list.add(root.val);}return list;}
}