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  1. /*The next palindrome*/
  2. #include<stdio.h>
  3. #include<string.h>
  4. #include<stdlib.h>
  5. #include<malloc.h>
  6.  
  7. #ifndef __cplusplus
  8. #define bool unsigned
  9. #define true 1
  10. #define false 0
  11. #endif    //__cplusplus
  12.  
  13. bool palin_more_than_org(const char* str,unsigned n)
  14. //str[i] gives palin, str[j] gives org
  15. {
  16. 	int i=n/2-1,j=(n+1)/2;
  17. 	for(;i>=0 && j<n;--i,++j)
  18. 	{
  19. 		if(str[j]>str[i])return false;
  20. 		else if(str[j]<str[i])return true;
  21. 	}
  22. 	return false;
  23. }
  24.  
  25. bool is_9s(const char* str,unsigned n)
  26. {
  27. 	unsigned i;
  28. 	for(i=0;i<n;++i)if(str[i]!='9')return false;
  29. 	return true;
  30. }
  31.  
  32. void next_palin(char* str,unsigned n)
  33. {
  34. 	unsigned i,j;
  35. 	if(is_9s(str,n))
  36. 	{
  37. 		str[0]='1';
  38. 		for(i=1;i<n;++i)str[i]='0';
  39. 		str[n]='1';
  40. 		str[n+1]='\0';
  41. 		return;
  42. 	}
  43. 	if(!palin_more_than_org(str,n))
  44. 	{
  45. 		//increase first half
  46. 		for(i=(n-1)/2;str[i]=='9';--i)str[i]='0';
  47. 		++str[i];
  48. 	}
  49. 	for(i=0,j=n-1;i<j;++i,--j)str[j]=str[i];
  50. }
  51.  
  52. int main()
  53. {
  54. 	unsigned i,t;
  55. 	char* str;
  56. 	scanf("%u",&t);
  57. 	//fflush(stdin);
  58. 	str=(char*)malloc(10000002);
  59. 	for(i=0;i<t;++i)
  60. 	{
  61. 		gets(str);
  62. 		next_palin(str,strlen(str));
  63. 		puts(str);
  64. 	}
  65. 	free(str);
  66. 	return 0;
  67. }
Success #stdin #stdout 0s 2856KB
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https://ideone.com/x2XQl2
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
secret

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