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  1. #include <algorithm>
  2. #include <string>
  3. #include <vector>
  4. #include <iostream>
  5.  
  6. using namespace std;
  7.  
  8. string theString;		//HACK
  9. int n;
  10. vector<vector<int> > _memo;
  11.  
  12. int f(int i, int j);		// Need forward declaration for mutual recursion
  13.  
  14. int m(int i, int j) {
  15. 	return static_cast<int>(theString[i - 1] == theString[j - 1] && i < j) + f(i - 1, j - 1);
  16. }
  17.  
  18. int f(int i, int j) {
  19. 	if (i == 0 || j == 0) {
  20. 		return 0;
  21. 	}
  22.  
  23. 	// Make sure the DP table is big enough
  24. 	if (_memo.size() <= i) {
  25. 		_memo.resize(i + 1);
  26. 	}
  27. 	if (_memo[i].size() <= j) {
  28. 		_memo[i].resize(j + 1, -1);		// -1 means "dunno yet"
  29. 	}
  30.  
  31. 	if (_memo[i][j] == -1) {
  32. 		// Dunno the answer yet, need to compute it
  33. 		_memo[i][j] = max(max(f(i - 1, j), f(i, j - 1)), m(i, j));
  34. 	}
  35.  
  36. 	return _memo[i][j];
  37. }
  38.  
  39. int longestSACS(string s) {
  40. 	// Clear the DP table
  41. 	_memo.clear();
  42. 	theString = s;
  43. 	n = theString.size();
  44.  
  45. 	int x = 0;
  46. 	for (int i = 0; i <= n; ++i) {
  47. 		x = max(x, f(i, n));
  48. 	}
  49.  
  50. 	return x;
  51. }
  52.  
  53. int main(int argc, char **argv) {
  54. 	cout << longestSACS("1213213515") << '\n';
  55. 	cout << longestSACS("1213243545") << '\n';
  56. 	return 0;
  57. }
  58.  
Success #stdin #stdout 0s 3416KB
comments (?)
stdin 
Standard input is empty
stdout 
6
5
https://ideone.com/I4CiJy
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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