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  1. #include <iostream>
  2. using namespace std;
  3. #include<bits/stdc++.h>
  4.  
  5. int main() {
  6. 	// your code goes here
  7. 	int n ; cin>>n;
  8. 	vector<int>arr(n);
  9. 	for(int i = 0 ;i<n;i++)cin>>arr[i];
  10. 	//p1 is prefix sum (maximum sub array sum ending at index i  
  11. 	vector<int>p1(n);
  12. 	p1[0]=arr[0];
  13. 	for(int i = 1 ; i< n ; i++){
  14. 		p1[i] = max({p1[i-1]+arr[i] , arr[i]});
  15. 	}
  16. 	//now create maximum subb array sum starting at index i ( p2 suffix sum )
  17. 	vector<int>p2(n);
  18. 	p2[n-1]=arr[n-1];
  19. 	for(int i = n-2;i>=0;i--){
  20. 		if(arr[i]<arr[i+1]){
  21. 			p2[i]=max(p2[i+1]+arr[i],arr[i]);
  22. 		}
  23. 		else {
  24. 			p2[i]=arr[i];
  25. 		}
  26. 	}
  27.  
  28. 	vector<int>max_p1(n); //max of max sub array sum ending at i 
  29. 	max_p1[0]=p1[0];
  30. 	for(int i = 1;i<n;i++){
  31. 		max_p1[i]=max(max_p1[i-1],p1[i]);
  32. 	}
  33. 	vector<int>max_p2(n); //max of max sub array sum starting at i 
  34. 	max_p2[n-1]=p2[n-1];
  35. 	for(int i = n-2;i>=0;i--){
  36. 		max_p2[i]=max(max_p2[i+1],p2[i]);
  37. 	}
  38. 	int max_sum = INT_MIN;
  39. 	for(int stick =0;stick<n-1;stick++){
  40. 		int left_maxsum = max_p1[stick];
  41. 		int right_maxsum=max_p2[stick+1];
  42. 		max_sum = max(left_maxsum+right_maxsum, max_sum);
  43. 	}
  44. 	cout<<max_sum;
  45. 	return 0;
  46. }
Success #stdin #stdout 0.01s 5328KB
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https://ideone.com/MBChMR
language:
C++ (gcc 8.3)
created:
1 day ago
visibility:
public

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