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  1. #include <iostream>
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. int main() {
  6. 	int n ; cin>>n;
  7. 	vector<int>arr(n);
  8. 	for(int i = 0 ; i<n;i++){
  9. 		cin>>arr[i];
  10. 	}
  11. 	vector<int>spre(n);
  12. 	spre[0]=0;
  13. 	for(int j = 1 ; j<n;j++){
  14. 		for(int i = 0 ; i<j;i++){
  15. 			if(arr[i]<arr[j]){
  16. 				spre[j]++;
  17. 			}
  18. 		}
  19. 	}
  20. 	vector<int>ssuf(n);
  21. 	ssuf[n-1]=0;
  22. 	for(int j = n-2 ; j>=0;j--){
  23. 		for(int i = n-1 ; i>j;i--){
  24. 			if(arr[i]<arr[j]){
  25. 				ssuf[j]++;
  26. 			}
  27. 		}
  28. 	}
  29.  
  30. 	int ans = 0 ; 
  31. 	for(int k = 0 ; k<n;k++){
  32. 		int left = 0 ; 
  33. 		int right = 0 ; 
  34. 		for(int j = 0 ; j<k;j++){
  35. 			if(arr[j]>arr[k]){
  36. 				left=left+spre[j];
  37. 			}
  38. 		}
  39. 		for(int l= k+1 ; l<n;l++){
  40. 			if(arr[l]>arr[k]){
  41. 				right=right+ssuf[l];
  42. 			}
  43. 		}
  44. 		ans+=left*right;
  45. 	}
  46. 	cout<<ans;
  47. 	// your code goes here
  48.  
  49.  
  50. 	return 0;
  51.  
  52. }
Success #stdin #stdout 0.01s 5328KB
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https://ideone.com/GXRYyy
language:
C++ (gcc 8.3)
created:
24 days ago
visibility:
public

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