Leetcode 145 Binary Tree Postorder Traversal

Author: jiajionline

0145_Binary Tree Postorder Traversal/BinaryTreePostorderTraversal_3.java

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+class Solution {
+ public List<Integer> postorderTraversal(TreeNode root) {
+ LinkedList<Integer> ans = new LinkedList<>();
+ if(root == null) return ans;
+ Deque<TreeNode> stack = new ArrayDeque<>();
+ stack.push(root);
+ while(!stack.isEmpty()) {
+ TreeNode node = stack.pop();
+ ans.addFirst(node.val);
+ if(node.left !=null) stack.push(node.left);
+ if(node.right != null) stack.push(node.right);
+ }
+ return ans;
+ }
+}