1 2 3 4 5
MergeItems←{,∘(+/)⌸/↓⍉⍺⍪⍵} ⎕←(↑(1 1) (2 1) (3 2)) MergeItems ↑(2 2) (1 3) ⎕←(↑(1 2) (2 3) (1 3) (3 2)) MergeItems ↑(3 1) (1 3) ⎕←(↑(1 1) (2 2) (3 3)) MergeItems ↑(2 3) (2 4)