1. 問題
2. コード
手が右回り・左回りのどちらを通るのかで、移動距離が変わります。
なので、まずは逆手が目的地までの間にあるかを調べ、あれば 0-N をまたぐルートになります。
;; ? x in [a, b] (not always a < b)
(defun in-range (x a b)
(or (<= a x b) (<= b x a)))
;; hand is symbol 'R or 'L read by (read)
(defun move-time-from-to (N left right hand to)
(let* ((from (if (eq hand 'R) right left))
(other (if (eq hand 'R) left right)))
(if (in-range other from to)
(- N (abs (- from to)))
(abs (- from to)))))Code language: Lisp (lisp)動かす手がどちらかは、’R, ‘L のシンボルでそのまま比較しています。
(defun in-range (x a b)
(or (<= a x b) (<= b x a)))
(defun move-time-from-to (N left right hand to)
(let* ((from (if (eq hand 'R) right left))
(other (if (eq hand 'R) left right)))
(if (in-range other from to)
(- N (abs (- from to)))
(abs (- from to)))))
;; (solve 6 '((R 4) (L 5) (R 6))) ;=> 8
(defun solve(N queries)
(loop for query in queries
with left = 1
with right = 2
with result = 0
do (let* ((hand (car query))
(to (cadr query)))
(incf result (move-time-from-to
N left right hand to))
(if (eq hand 'R)
(setf right to)
(setf left to)))
finally (return result)))
(defun main ()
(let* ((N (read))
(Q (read))
(queries (loop repeat Q
collect (list (read) (read)))))
(princ (solve N queries))))
#-swank(main)Code language: Lisp (lisp)