AtCoder adt_easy_20260508_1

1. A – Repdigit

• A – Repdigit

;; (repdigit-p 111) ;=> T
;; (repdigit-p 100) ;=> NIL
(defun repdigit-p (n)
  (labels ((rec (n d)
             (cond
               ((= n 0) t)
               ((= (mod n 10) d)
                (rec (floor n 10) d))
               (t nil))))
    (rec n (mod n 10))))

(defun print-yesno (c)
  (declare (type boolean c))
  (princ (if c "Yes" "No")))

(defun main ()
  (print-yesno (repdigit-p (read))))

#-swank(main)
Code language: PHP (php)

2. B – Isosceles

• B – Isosceles

;; (isosceles-p 4 2 4) ;=> T
(defun isosceles-p (a b c)
  (or (= a b) (= a c) (= b c)))


(defun print-yesno (c)
  (declare (type boolean c))
  (princ (if c "Yes" "No")))

(defun main ()
  (print-yesno (isosceles-p (read) (read) (read))))

#-swank(main)Code language: PHP (php)

3. C – Election

• C – Election

;; (elected-name '("x" "y" "xx" "y" "z")) ; => "y"
(defun elected-name (names)
  (let ((ht (make-hash-table :test #'equal)))
    (loop for name in names
          do (setf (gethash name ht 0) 
                   (1+ (gethash name ht 0))))
    (loop for name being each hash-key of ht
            using (hash-value voted)
          with max = 0
          with result = ""
          when (< max voted)
            do (setf result name)
               (setf max voted)
          finally (return result))))

(defun main ()
  (let* ((n (read))
         (names (loop repeat n collect (read-line))))
    (princ (elected-name names))))

#-swank(main)Code language: PHP (php)

4. D – Same Name

• D – Same Name

(defun same-name-p (names)
  (let ((ht (make-hash-table :test #'equal)))
    (loop for name in names
          do (setf (gethash name ht 0) 
                   (1+ (gethash name ht 0))))
    (loop for name being each hash-key of ht
            using (hash-value number)
          thereis (>= number 2))))

;; (same-names '("tanaka taro" "sato hanako" "tanaka taro")) ;=> T

(defun print-yesno (c)
  (declare (type boolean c))
  (princ (if c "Yes" "No")))

(defun main ()
  (let* ((n (read))
         (names (loop repeat n collect n)))
    (print-yesno (same-name-p names))))

#-swank(main)

Code language: PHP (php)

5. E – Spiral Rotation

• E – Spiral Rotation

(defun read-lines (N)
  (loop for row below N
        collect (read-line)))

(defun make-grid (N lines)
  (let ((grid (make-array (list N N)
                          :element-type 'character
                          :initial-element #\.)))
    (loop for row below N
          for line in lines
          do (loop for ch across line
                   for col below N
                   do (setf (aref grid row col) ch))
          finally (return grid))))

(defun make-grid (N lines)
  (let ((grid (make-array (list N N)
                          :element-type 'character
                          :initial-element #\.)))
    (loop for row below N
          for line in lines
          do (loop for ch across line
                   for col below N
                   do (setf (aref grid row col) ch))
          finally (return grid))))

(defun copy-grid! (N from to)
  (loop for row below N
        do (loop for col below N
                 do (setf (aref to row col)
                          (aref from row col)))
        finally (return to)))


(defun manipulate! (N grid temp i)
  (copy-grid! N grid temp)
    (loop for x from i to (+ N 1 (- i))
        do (loop for y from i to (+ N 1 (- i))
                 do (setf (aref grid (1- y) (- N x))
                          (aref temp (1- x) (1- y)))))
  grid)

(defun manipulate-times! (N grid)
  (let ((temp (make-array (list N N)
                          :element-type 'character
                          :initial-element #\.)))
    (loop for i from 1 to (floor N 2)
          do (manipulate! N grid temp i))
    grid))

(defun print-grid (N grid)
  (loop for x from 1 to N
        do (loop for y from 1 to N
                 do (princ (aref grid (1- x) (1- y))))
           (terpri)))

(defun main ()
  (let* ((n (read))
         (lines (read-lines n))
         (grid (make-grid n lines))
         )
    (print-grid n (manipulate-times! n grid))))

#-swank(main)
Code language: PHP (php)

6.