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  1. #include <iostream>
  2. #include <cstdlib>
  3. #include <cstring>
  4. #include <ctime>
  5. using namespace std;
  6.  
  7. const int max_n = 50;
  8. int memo[max_n];
  9.  
  10. int count(int n)
  11. {
  12. 	if (n == 0)
  13. 		return 1;
  14.  
  15. 	int &ans = memo[n];
  16. 	if (ans != -1)
  17. 		return ans;
  18.  
  19. 	ans = 0;
  20. 	for (int i = 0; i < n; ++i)
  21. 		ans += count(i) * count(n - 1 - i);
  22.  
  23. 	return ans;
  24. }
  25.  
  26. void bracket(int n)
  27. {
  28. 	if (n == 0)
  29. 		return;
  30.  
  31. 	int r = rand() % count(n);
  32. 	int left_len = 0;
  33. 	while (r >= count(left_len) * count(n - 1 - left_len)) {
  34. 		r -= count(left_len) * count(n - 1 - left_len);
  35. 		++left_len;
  36. 	}
  37. 	int right_len = n - 1 - left_len;
  38.  
  39.  
  40. 	cout << '(';
  41. 	bracket(left_len);
  42. 	cout << ')';
  43. 	bracket(right_len);
  44. }	
  45.  
  46. int main()
  47. {
  48. 	srand(time(NULL));
  49.  
  50. 	int n;
  51. 	cin >> n;
  52.  
  53. 	memset(memo, -1, sizeof memo);
  54.  
  55. 	bracket(n);
  56.  
  57. 	return 0;
  58. }
Success #stdin #stdout 0s 3416KB
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https://ideone.com/xbFP8h
language:
C++ (gcc 8.3)
created:
8 years ago
visibility:
secret

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