https://leetcode.com/problems/binary-tree-postorder-traversal/
题意
后序遍历树，非递归实现，基本跟144一致，只是最后结果需要reverse一下，但是速度比较慢
class Solution { List<Integer> results = new ArrayList<>(); Stack<TreeNode> stacks = new Stack<>(); public List<Integer> postorderTraversal(TreeNode root) { if (root == null) { return results; } stacks.push(root); while (!stacks.isEmpty()) { TreeNode current = stacks.pop(); results.add(current.val); if (current.right != null) { stacks.push(current.right); } if (current.left != null) { stacks.push(current.left); } } Collections.reverse(results); return results; } }