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  1. #include<stdio.h>
  2. #include<stdlib.h>
  3.  
  4. int checkifsafe(char *s)
  5. {
  6. 	int sum =0;
  7. 	while(*s)
  8. 	{
  9. 		*s++=='{'?sum++:sum--;
  10. 		if(sum<-1)
  11. 			return 0;
  12. 	}
  13. 	return 1;
  14. }
  15.  
  16. void printset(char *s)
  17. {
  18. 	if(checkifsafe(s))
  19. 	{
  20. 		printf("{");
  21. 		while(*s)
  22. 			printf("%c",*s++);
  23. 		printf("}\n");
  24. 	}
  25. }
  26.  
  27. void initialize(char *s,int n)
  28. {
  29. 	int i;
  30. 	for(i=0;i<n;i++)
  31. 	{
  32. 		s[i] = '{';
  33. 		s[i + n] = '}';
  34. 	}
  35. 	s[2*n] = '\0';
  36. }
  37.  
  38. void swap(char *a,char *b)
  39. {
  40. 	char t = *a;
  41. 	*a = *b;
  42. 	*b = t;
  43. }
  44.  
  45. int check(char *s,int i,int c)
  46. {
  47. 	int j;
  48. 	for(j=c;j<i;j++)
  49. 	{
  50. 		if(s[j]==s[i])
  51. 			return 0;
  52. 	}
  53. 	return 1;
  54. }
  55.  
  56. void permute(char *s, int c, int n)
  57. {
  58. 	int i;
  59. 	if(c>=n-1)
  60. 		printset(s);
  61. 	else
  62. 	{
  63. 		for(i=c;i<n;i++)
  64. 		{
  65. 			if(check(s,i,c) || i==c)
  66. 			{
  67. 				swap(s+i,s+c);
  68. 				permute(s,c+1,n);
  69. 				swap(s+i,s+c);
  70. 			}
  71. 		}
  72. 	}
  73. }
  74.  
  75. int main(int argc,int **argv)
  76. {
  77. 	int n;
  78. 	printf("enter set number\n");
  79. 	scanf("%d",&n);
  80. 	n--;
  81. 	char *s = (char *)malloc(sizeof(2*n+1));
  82. 	initialize(s,n);
  83. 	permute(s,0,2*n);
  84. 	return 0;
  85. }
  86.  
stdin 
5
compilation info 
prog.c:75: warning: second argument of ‘main’ should be ‘char **’
prog.c: In function ‘main’:
prog.c:79: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result
stdout 
enter set number
{{{{{}}}}}
{{{{}{}}}}
{{{{}}{}}}
{{{{}}}{}}
{{{{}}}}{}
{{{}{{}}}}
{{{}{}{}}}
{{{}{}}{}}
{{{}{}}}{}
{{{}}{{}}}
{{{}}{}{}}
{{{}}{}}{}
{{{}}}{{}}
{{{}}}{}{}
{{}{{{}}}}
{{}{{}{}}}
{{}{{}}{}}
{{}{{}}}{}
{{}{}{{}}}
{{}{}{}{}}
{{}{}{}}{}
{{}{}}{{}}
{{}{}}{}{}
{{}}{{{}}}
{{}}{{}{}}
{{}}{{}}{}
{{}}{}{{}}
{{}}{}{}{}
{}{{{{}}}}
{}{{{}{}}}
{}{{{}}{}}
{}{{{}}}{}
{}{{}{{}}}
{}{{}{}{}}
{}{{}{}}{}
{}{{}}{{}}
{}{{}}{}{}
{}{}{{{}}}
{}{}{{}{}}
{}{}{{}}{}
{}{}{}{{}}
{}{}{}{}{}
https://ideone.com/AgFeH
language:
C (gcc 8.3)
created:
14 years ago
visibility:
public

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