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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n; cin >> n;
  6. 	vector<int> arr(n);
  7. 	for(int i = 0; i < n; i++)
  8. 	cin >> arr[i];
  9.  
  10. 	vector<int> diff(n);
  11. 	for(int i = 1; i < n; i++){
  12. 		diff[i] = arr[i] - arr[i-1];
  13. 	}
  14. 	vector<int> pref(n);
  15. 	vector<int> suff(n);
  16. 	pref[1] = 1;
  17. 	int len = INT_MIN;
  18. 	for(int i = 2; i < n; i++){
  19. 		if(diff[i] == diff[i-1])
  20. 		pref[i] = pref[i-1]+1;
  21. 		else
  22. 		pref[i] = 1;
  23.  
  24. 		len = max(len, pref[i]);
  25. 	}
  26. 	suff[n-1] = 1;
  27. 	for(int i = n-2; i >= 1; i--){
  28. 		if(diff[i] == diff[i+1])
  29. 		suff[i] = suff[i+1]+1;
  30. 		else
  31. 		suff[i] = 1;
  32. 	}
  33. 	int max_len = 0;
  34. 	for(int i = 1; i < n; i++){
  35. 		if(abs(diff[i]) == abs(diff[i+1])){
  36. 			if(i >=2 && i < n-2)
  37. 			max_len = pref[i-1]+suff[i+2]+2;
  38. 			else if(i < n-2)
  39. 			max_len = suff[i+2]+3;
  40. 			else if(i >= 2)
  41. 			max_len = suff[i+2]+3;
  42. 			else
  43. 			max_len = 2;
  44.  
  45. 			len = max(len, max_len);
  46. 		}
  47. 	}
  48. 	cout << len+1;
  49. 	return 0;
  50. }
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/ctLPji
language:
C++14 (gcc 8.3)
created:
7 days ago
visibility:
public

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