## [leetcode] Binary Tree Postorder Traversal

Binary Tree Postorder Traversal Given a binary tree, return the postorder traversal of its nodes’ values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [3,2,1]. Note: Recursive solution is trivial, could you do it iteratively? Use two stacks to simulate recursion. stack st stores visiting nodes, […]