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  1. #include <cstring>
  2. #include <iostream>
  3. using namespace std;
  4.  
  5. #define ll long long
  6.  
  7. ll memo[2000][4][4];
  8.  
  9. ll dp(int col, int drow, int grow) {
  10. 	// row out of bound
  11. 	if (drow < 0 || 4 <= drow || grow < 0 || 4 <= grow)
  12. 		return 0;
  13. 	// d crossed with g
  14. 	if (grow <= drow)
  15. 		return 0;
  16. 	// first column
  17. 	if (col == 1) {
  18. 		if (drow == 0 && grow == 3)
  19. 			return 1;
  20. 		else
  21. 			return 0;
  22. 	}
  23. 	if (memo[col][drow][grow] != -1)
  24. 		return memo[col][drow][grow];
  25.  
  26. 	memo[col][drow][grow] = 0;
  27. 	memo[col][drow][grow] += dp(col-1, drow-1, grow-1);
  28. 	memo[col][drow][grow] += dp(col-1, drow-1, grow+1);
  29. 	memo[col][drow][grow] += dp(col-1, drow+1, grow-1);
  30. 	memo[col][drow][grow] += dp(col-1, drow+1, grow+1);
  31. 	memo[col][drow][grow] = memo[col][drow][grow] % 7;
  32.  
  33. 	return memo[col][drow][grow];
  34. }
  35.  
  36. int main() {
  37. 	int N;
  38. 	cin >> N;
  39. 	memset(memo, -1, sizeof(memo));
  40. 	ll ans = 0;
  41. 	for (int i = 0; i < 4; i++)
  42. 		for (int j = i+1; j < 4; j++)
  43. 			ans += dp(N, i, j);
  44. 	cout << ans % 7 << endl;
  45. }
Success #stdin #stdout 0.01s 5532KB
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https://ideone.com/Q75CQB
language:
C++ (gcc 8.3)
created:
2 years ago
visibility:
secret

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