APL
Under ⍢
_U_ ← {⍵⍵⍣¯1⊢ ⍺⍺ ⍵⍵ ⍵}
_U_ ← {⍺←{⍵ ⋄ ⍺⍺} ⋄ ⍵⍵⍣¯1⊢(⍵⍵ ⍺)⍺⍺(⍵⍵ ⍵)}
Use zero-indexing
⎕IO ← 0
Output visualization
]box on -style=max
]boxing off
Under ⍢
_U_ ← {⍵⍵⍣¯1⊢ ⍺⍺ ⍵⍵ ⍵}
_U_ ← {⍺←{⍵ ⋄ ⍺⍺} ⋄ ⍵⍵⍣¯1⊢(⍵⍵ ⍺)⍺⍺(⍵⍵ ⍵)}
Use zero-indexing
⎕IO ← 0
Output visualization
]box on -style=max
]boxing off