Submission #7316846

---

Source Code Expand

;; -*- coding: utf-8 -*-
(eval-when (:compile-toplevel :load-toplevel :execute)
  (sb-int:defconstant-eqx OPT
    #+swank '(optimize (speed 3) (safety 2))
    #-swank '(optimize (speed 3) (safety 0) (debug 0))
    #'equal)
  #+swank (ql:quickload '(:cl-debug-print :fiveam) :silent t)
  #-swank (set-dispatch-macro-character
           #\# #\> (lambda (s c p) (declare (ignore c p)) (read s nil (values) t))))
#+swank (cl-syntax:use-syntax cl-debug-print:debug-print-syntax)
#-swank (disable-debugger) ; for CS Academy

;; BEGIN_INSERTED_CONTENTS
;;;
;;; ARRAY-ELEMENT-TYPE is not constant-folded on SBCL version earlier than
;;; 1.5.0. See
;;; https://github.com/sbcl/sbcl/commit/9f0d12e7ab961828931d01c0b2a76a5885ad35d2
;;;

(eval-when (:compile-toplevel :load-toplevel :execute)
  (sb-c:deftransform array-element-type ((array))
    (let ((type (sb-c::lvar-type array)))
      (flet ((element-type (type)
               (and (sb-c::array-type-p type)
                    (sb-int:neq (sb-kernel::array-type-specialized-element-type type) sb-kernel:*wild-type*)
                    (sb-kernel:type-specifier (sb-kernel::array-type-specialized-element-type type)))))
        (cond ((let ((type (element-type type)))
                 (and type
                      `',type)))
              ((sb-kernel:union-type-p type)
               (let (result)
                 (loop for type in (sb-kernel:union-type-types type)
                       for et = (element-type type)
                       unless (and et
                                   (if result
                                       (equal result et)
                                       (setf result et)))
                       do (sb-c::give-up-ir1-transform))
                 `',result))
              ((sb-kernel:intersection-type-p type)
               (loop for type in (sb-kernel:intersection-type-types type)
                     for et = (element-type type)
                     when et
                     return `',et
                     finally (sb-c::give-up-ir1-transform)))
              (t
               (sb-c::give-up-ir1-transform)))))))

;;;
;;; 2D convex hull of points (Monotone Chain Algorithm)
;;; Complexity: O(nlog(n))
;;;

(declaim (inline make-convex-hull!))
(defun make-convex-hull! (points &optional (eps 0))
  "Returns the vector of the vertices of the convex hull, which are sorted in
the anticlockwise direction around the perimeter. This function sorts POINTS as
a side effect.

If EPS is non-negative, three vertices in a straight line are excluded (when the
calculation error is within EPS, of course); they are allowed if EPS is
negative.

POINTS := vector of complex number"
  (declare (inline sort)
           (vector points))
  ;; FIXME: the returned vector may contain duplicate vertices in a degenerative
  ;; case: E.g. (make-convex-hull! #(#c(1 2) #c(1 2) #c(1 2) #c(1 2)) ) |->
  ;; #(#C(1 2) #C(1 2))
  (macrolet ((outer (p1 p2) ; outer product
               `(let ((c1 ,p1)
                      (c2 ,p2))
                  (- (* (realpart c1) (imagpart c2))
                     (* (imagpart c1) (realpart c2))))))
    (when (<= (length points) 1)
      (return-from make-convex-hull! (copy-seq points)))
    (let* ((n (length points))
           (end 0)
           (res (make-array (* n 2) :element-type (array-element-type points)))
           (points (sort points (lambda (p1 p2)
                                  (if (= (realpart p1) (realpart p2))
                                      (< (imagpart p1) (imagpart p2))
                                      (< (realpart p1) (realpart p2)))))))
      (declare (fixnum end))
      (do ((i 0 (+ i 1)))
          ((= i n))
        (loop (if (and (> end 1)
                       (<= (outer (- (aref res (- end 1)) (aref res (- end 2)))
                                  (- (aref points i) (aref res (- end 1))))
                           eps))
                  (decf end)
                  (return)))
        (setf (aref res end) (aref points i))
        (incf end))
      (let ((tmp-end end))
        (do ((i (- n 2) (- i 1)))
            ((< i 0))
          (loop (if (and (> end tmp-end)
                         (<= (outer (- (aref res (- end 1)) (aref res (- end 2)))
                                    (- (aref points i) (aref res (- end 1))))
                             eps))
                    (decf end)
                    (return)))
          (setf (aref res end) (aref points i))
          (incf end)))
      (adjust-array res (- end 1)))))

(defmacro dbg (&rest forms)
  #+swank
  (if (= (length forms) 1)
      `(format *error-output* "~A => ~A~%" ',(car forms) ,(car forms))
      `(format *error-output* "~A => ~A~%" ',forms `(,,@forms)))
  #-swank (declare (ignore forms)))

(defmacro define-int-types (&rest bits)
  `(progn
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "UINT~A" b)) () '(unsigned-byte ,b))) bits)
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "INT~A" b)) () '(signed-byte ,b))) bits)))
(define-int-types 2 4 7 8 15 16 31 32 62 63 64)

(declaim (inline println))
(defun println (obj &optional (stream *standard-output*))
  (let ((*read-default-float-format* 'double-float))
    (prog1 (princ obj stream) (terpri stream))))

(defconstant +mod+ 1000000007)

;;;
;;; Body
;;;

(defconstant +eps+ 1d-9)

(defun main ()
  (let* ((n (read))
         (vecs (make-array n :element-type '(complex double-float)))
         (dp (make-array 1 :element-type '(complex double-float) :initial-element #c(0d0 0d0))))
    (dotimes (i n)
      (let* ((x (float (read) 1d0))
             (y (float (read) 1d0)))
        (setf (aref vecs i) (complex x y))))
    (dotimes (i n)
      (let* ((v (aref vecs i))
             (len (length dp))
             (translation (adjust-array dp (* 2 len))))
        (declare ((simple-array (complex double-float) (*)) translation)
                 (uint32 len))
        (dotimes (i len)
          (setf (aref translation (+ i len))
                (+ (aref translation i) v)))
        (setq dp (make-convex-hull! translation +eps+))))
    (println (reduce #'max dp :key #'abs))))

#-swank (main)

Submission Info

Judge Result