力扣 145. 二叉树的后序遍历 递归 迭代
递归
/**
* 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> result = new ArrayList<>();
preorder(root,result);
return result;
}
void preorder(TreeNode root,List<Integer> result){
if(root==null){
return;
}
preorder(root.left,result);
preorder(root.right,result);
result.add(root.val);
}
}
迭代