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  1. #include<stdio.h>
  2. #include<string.h>
  3.  
  4. #define MOD 1000000007
  5. long long fact(long long x)
  6. {
  7. 	long long f=1;
  8. 	if(x==0)
  9. 		return 1;
  10. 	else
  11. 	{
  12. 		for(int i=1;i<=x;i++)
  13. 			//f=f*(i%MOD);		//mod was used in a wrong way 
  14. 			f=((f*i)%MOD);		//always use it as shown here 
  15. 	}
  16. 	return f%MOD;
  17. }
  18. long long square(long long x)
  19. {
  20. 	//return x*x;		//mod was missing here
  21. 	return (x*x)%MOD;
  22. }
  23. long long power(long long base,long long expo)
  24. {
  25. 	if(base==0)
  26. 		return 0;
  27. 	if(expo==0)
  28. 		return 1;
  29. 	else
  30. 	{
  31. 		if(expo%2==0)
  32. 			return square(power(base,expo/2))%MOD;
  33. 		else
  34. 			return (base*power(base,expo-1))%MOD;
  35. 	}
  36. }
  37. int main()
  38. {
  39. 	int arr[26]={0};
  40. 	char ip[1000000];
  41. 	scanf("%s",ip);
  42. 	long long num,den=1;
  43. 	int len=strlen(ip);
  44. 	for(int i=0;i<len;i++)
  45. 		arr[ip[i]-'a']++;
  46. 	for(int i=0;i<26;i++)
  47. 		arr[i]/=2;
  48. 	num=fact(len/2);
  49.  
  50. 	for(int i=0;i<26;i++)
  51. 	{
  52. 		//den=den*(fact(arr[i]));		//again mod was missing here
  53. 		den=(den*(fact(arr[i])))%MOD;
  54. 	}
  55. 	den=den%MOD;
  56. 	den=power(den,MOD-2);
  57. 	printf("%lld\n",((num%MOD)*(den%MOD))%MOD);
  58. 	//printf("%lld",fact((long long)5));
  59. }
Success #stdin #stdout 0s 3152KB
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https://ideone.com/DZrqwO
language:
C99 (gcc 8.3)
created:
9 years ago
visibility:
public

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