A complete binary tree has a restricted shape obtained by starting at the root and filling the tree by levels from left to right. In the complete binary tree of height d, all levels except possibly level d are completely full. If an inorder traversal of a complete binary tree visits the nodes in the order ABCDEF (where each letter is the value of a node), which order are the nodes visited during an postorder traversal?

ACBEFD
  • DBACFE
  • DBFACE
  • DEBFCA
  • ABDECF
  • DBACFE

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