Binary Tree postorder Traversal

http://bookshadow.com/weblog/2015/01/19/leetcode-binary-tree-postorder-traversal/

http://bookshadow.com/weblog/2015/01/19/binary-tree-post-order-traversal/

Don't remember AH always, better try double stack method, borrow as above link hint, reverse preorder

Pay attention to the left and right order of the child nodes when pressed into the stack

 Public classSolution { PublicArraylist<integer>postordertraversal (TreeNode root) {ArrayList<Integer> res =NewArraylist<integer>(); if(root==NULL)returnRes; Stack<TreeNode> st =NewStack<treenode>(); Stack<TreeNode> out=NewStack<treenode>();        St.push (root);  while(!St.isempty ()) {TreeNode n=St.pop ();            Out.push (n); if(n.left!=NULL) {St.push (n.left); }            if(n.right!=NULL) {St.push (n.right); }        }         while(!Out.isempty ()) {TreeNode o=Out.pop ();        Res.add (O.val); }        returnRes; }}

Binary Tree postorder Traversal