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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <cmath>
  4. using namespace std;
  5.  
  6. int main() { 
  7. 	int n, x1, x2, y1, y2, x, y; 
  8. 	double sum=0; 
  9. 	cin >> n >> x >> y; 
  10. 	x1=x; 
  11. 	y1=y; 
  12. 	for (int i=0; i<(n-1); i++) { 
  13. 		cin >> x2 >> y2; 
  14. 		sum=sum+(x1+x2)*(y2-y1); 
  15. 		x1=x2; 
  16. 		y1=y2; 
  17. 	} 
  18. 	sum=sum+(x+x2)*(y-y2); 
  19. 	cout << fixed << setprecision(3) << abs(sum) / 2 << endl;
  20. 	return 0; 
  21. }
Success #stdin #stdout 0s 3416KB
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https://ideone.com/vPR8n1
language:
C++14 (clang 8.0)
created:
9 years ago
visibility:
secret

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