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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <algorithm>
  5.  
  6. long long *NearestPalindromeNumbers(long long n)
  7. {
  8.     char s[32];
  9.     static long long x[3];
  10.  
  11.     int k = sprintf(s, "%lld", n);
  12.     int j = k / 2;
  13.     int i = k - j;
  14.     strncpy(s + i, s, j)[j] = 0;
  15.     std::reverse(s + i, s + k);
  16.     x[0] = atoll(s);
  17.     if (x[0] == n) return x[1] = -1, x;
  18.  
  19.     s[i] = 0;
  20.     k = sprintf(s, "%lld", atoll(s) + (x[0] < n ? 1 : -1));
  21.     if (strcmp(s, "0") == 0) strcpy(s, "9"), j--;
  22.     if (k < i) strcat(s, "9"), j--;
  23.     strncpy(s + i, s, j)[j] = 0;
  24.     std::reverse(s + i, s + i + j);
  25.     x[1] = atoll(s);
  26.  
  27.     long long d = abs(x[0] - n) - abs(x[1] - n);
  28.     if (d < 0) return x[1] = -1, x;
  29.     if (d > 0) return x[2] = -1, x + 1;
  30.     return x[0] < x[1] ? x : (x[2] = x[0], x + 1);
  31. }
  32.  
  33. int main(void)
  34. {
  35.     long long q[] = {0, 5, 10, 17, 100, 1000, 2024, 12345679042654321};
  36.  
  37.     for (int i = 0; i < sizeof(q) / sizeof(*q); i++) {
  38.         long long *x = NearestPalindromeNumbers(q[i]);
  39.         for (int j = 0; j < 2; j++) if (x[j] >= 0) printf("%s%lld", j ? ", " : "[", x[j]);
  40.         printf("]\n");
  41.     }
  42.     return 0;
  43. }
  44.  
Success #stdin #stdout 0s 5296KB
comments (?)
stdin 
Standard input is empty
stdout 
[0]
[5]
[9, 11]
[22]
[99, 101]
[999, 1001]
[2002]
[12345678987654321, 12345679097654321]
https://ideone.com/e1AM8A
language:
C++ 4.3.2 (gcc-4.3.2)
created:
89 days ago
visibility:
secret

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