InvertTree←{

⍝ ⍵: Full binary tree in the format
⍝ Node number (ID), value, parent
⍝
⍝       1
⍝      /  \
⍝     2    3
⍝    / \  / \
⍝   4   5 6  7
⍝
⍝ For example, the above tree in depth-first pre-order traversal
⍝ n ← 0 1 2 3 4 5 6
⍝ v ← 1 2 4 5 3 6 7
⍝ p ← 0 0 1 1 0 4 4
     (n v p)←⍵

     TreeMatrix←{
    ⍝ Binary matrix for a full binary tree
    ⍝ Each row is a binary mask for elements on that row
    ⍝
    ⍝ For the example tree:
    ⍝       v⌿⍤1⍨ TreeMatrix p
    ⍝ 1 0 0 0
    ⍝ 2 3 0 0
    ⍝ 4 5 6 7
    ⍝
         ⎕IO←0
         ⍺←0
         r←⍵(∨⌿∘.=)⍨,⍺
         c←⍸r
         0≡⍺:(↑1(0@0⊢r))⍪(1↓c)∇ ⍵
         ⍬≡c:⍬⍴⍨0,⍴⍵
         r⍪(c ∇ ⍵)
     }
     InvertValues←{
     ⍝ Horizontally flip values at each level of the tree
         ⍵≡⍬⍴⍨0,⊃⌽⍴⍵:⍺       ⍝ No more rows: Return inverted values
         (⌽@(⍸1⌷⍵)⊢⍺)∇ 1↓⍵   ⍝ Horizontal flip ∇ Recurse remaining levels / rows
     }
     iv←v InvertValues TreeMatrix p
     (n iv p) ⍝ Return inverted tree

 }