Language: C C++ D Haskell Lua OCaml PHP Perl Plain Text Python Ruby Scheme Tcl ; unwrapping a spiral (define (matrix-rows x) (vector-length x)) (define (matrix-cols x) (vector-length (vector-ref x 0))) (define (matrix-ref m i j) (vector-ref (vector-ref m i) j)) (define (spiral m) (let ((r (matrix-rows m)) (c (matrix-cols m))) (let loop ((x -1) (y 0) (dx 1) (dy 0) (r r) (c c) (i 0) (xs '())) (cond ((zero? r) (reverse xs)) ((= i c) (loop x y (- dy) dx c (- r 1) 0 xs)) (else (let ((x (+ x dx)) (y (+ y dy))) (loop x y dx dy r c (+ i 1) (cons (matrix-ref m y x) xs)))))))) (display (spiral #( #( 1 2 3 4) #( 5 6 7 8) #( 9 10 11 12) #(13 14 15 16) #(17 18 19 20)))) Private [?] Run code