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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <math.h>
  5. #include <ctype.h>
  6.  
  7. int const max = 'Z'-'A' + 1;
  8.  
  9. static char const*
  10. encode(char* buf, size_t bufsize, int n) {
  11. 	char* beg = buf;
  12. 	char* cur = buf+bufsize-1;
  13.  
  14. 	*beg = *cur = '\0';
  15.  
  16. 	while (n > 0 && cur > beg) {
  17. 		int r = (n%max);
  18. 		if (r == 0) {
  19. 			n /= max;
  20. 			n--;
  21. 			r = max;
  22. 		} else
  23. 			n /= max;
  24. 		*(--cur) = 'A'-1+r;
  25. 	}
  26. 	return cur;
  27. }
  28.  
  29. static int
  30. decode(char const* str) {
  31. 	char const* beg = str;
  32. 	char const* end = beg+strlen(str)-1;
  33. 	int n = 0;
  34.  
  35. 	while (beg < end) {
  36. 		n += pow(max, end-beg) * (*beg-'A'+1);
  37. 		++beg;
  38. 	}
  39. 	n += ((*end)-'A'+1);
  40. 	return n;
  41. }
  42.  
  43. int
  44. main(void) {
  45. 	char line[128];
  46. 	char buf[10];
  47.  
  48. 	while (fgets(line, sizeof line, stdin)) {
  49. 		size_t len=strlen(line);
  50. 		if (line[len-1] == '\n')
  51. 			line[len-1] = '\0';
  52.  
  53. 		printf("'%s' convert to\n", line);
  54. 		if (isalpha(line[0])) {
  55. 			int n = decode(line);
  56. 			printf("decode value: '%d'\n", n);
  57. 			printf("encode value: '%s'\n", encode(buf, sizeof buf, n));		
  58. 		} else {
  59. 			int n = atoi(line);
  60. 			char const* p;
  61. 			printf("encode value: '%s'\n", p=encode(buf, sizeof buf, n));					
  62. 			printf("decode value: '%d'\n", decode(p));
  63. 		}
  64. 		puts("");
  65. 	}
  66. 	return 0;
  67. }
  68.  
Success #stdin #stdout 0s 2056KB
comments (?)
stdin
copy 
A
Z
AA
ZZ
DBA
AAZ
ZZZ
2757
125
stdout
copy 
'A' convert to
decode value: '1'
encode value: 'A'

'Z' convert to
decode value: '26'
encode value: 'Z'

'AA' convert to
decode value: '27'
encode value: 'AA'

'ZZ' convert to
decode value: '702'
encode value: 'ZZ'

'DBA' convert to
decode value: '2757'
encode value: 'DBA'

'AAZ' convert to
decode value: '728'
encode value: 'AAZ'

'ZZZ' convert to
decode value: '18278'
encode value: 'ZZZ'

'2757' convert to
encode value: 'DBA'
decode value: '2757'

'125' convert to
encode value: 'DU'
decode value: '125'
https://ideone.com/LsH7Hf
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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