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  1. (defun nearest-palindromic-numbers (n &key (radix 10))
  2.   (check-type n integer)
  3.   (if (< n radix)
  4.       (list (max 0 n))
  5.       (block nil
  6.         (let* ((s (format nil "~vR" radix n))
  7.                (len (length s))
  8.                a-len b-len a b x y d)
  9.           (when (= n (expt radix (1- len)))
  10.             (return (list (1- n) (1+ n))))
  11.           (setq b-len (floor len 2)
  12.                 a-len (- len b-len)
  13.                 a (subseq s 0 a-len)
  14.                 b (reverse (subseq s 0 b-len))
  15.                 x (parse-integer (format nil "~A~A" a b) :radix radix))
  16.           (when (= x n)
  17.             (return (list x)))
  18.           (setq a (format nil "~vR" radix
  19.                           (+ (parse-integer a :radix radix)
  20.                              (if (< x n) 1 -1)))
  21.                 b (reverse (subseq a 0 b-len))
  22.                 y (parse-integer (format nil "~A~A" a b) :radix radix)
  23.                 d (- (abs (- x n))
  24.                      (abs (- y n))))
  25.           (cond ((< d 0) (list x))
  26.                 ((> d 0) (list y))
  27.                 ((< x y) (list x y))
  28.                 (t (list y x)))))))
  29.  
  30. (loop with radix = 10
  31.       for line = (read-line nil nil)
  32.       for n = (and line (parse-integer line :radix radix))
  33.       while n
  34.       do (format t "~{~A~^, ~}~%"
  35.                  (mapcar (lambda (p) (format nil "~vR" radix p))
  36.                          (nearest-palindromic-numbers n :radix radix))))
  37.  
Success #stdin #stdout 0.01s 30540KB
comments (?)
stdin 
0
5
17
100
2024
123459321
31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989
stdout 
0
5
22
99, 101
2002
123454321, 123464321
31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491319491103818397221984272575881537659472699732644708458115013971162391837116812903591959575630727503349061151491596414831256640288450350331100630952987634635171904529282690290251884718855136066007854273721419420627063933128466234540168430643296658465419091021725613876873328465748216443395665790188244691830394598492264469555011258391072014820547111848218049535271322850559064483907466032823156808412897607112435284308268998026826046187032954494790285015739939617914882059723833462648323979853562951413
https://ideone.com/CUPTas
language:
Common Lisp (sbcl 1.4.16)
created:
88 days ago
visibility:
public

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