If pre order traversal of a binary tree output 15,10,12,11,20,17,19 Find the order of postorder traversal of the tree 10,11,12,15,16,18,19,20 19,16,18,20,11,20,10,15 20,16,18,16,12,11,15,10 11,12,10,16,19,18,20,15