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  1. #include <iostream>
  2. #include <math.h>
  3. using namespace std;
  4. int f (int x, int x0, int x1, int y, int y0, int y1)
  5. {
  6. 	return  (x - x0) * (y1 - y0) - (y - y0) * (x1 - x0);
  7. } 
  8. int main() {
  9. 	double xa, ya, xb, yb, xc, yc, xd, yd;
  10. 	cin >> xa >> ya >> xb >> yb >> xc >> yc >> xd >> yd;
  11. 	int l,m;
  12. 	l = f(xc,xb,xa,yc,yb,ya);
  13. 	m = f(xd,xb,xa,yd,yb,ya);
  14. 	if (l * m < 0) {
  15. 		printf("не выпуклый");
  16. 		return 0;
  17. 	}
  18. 	int q,w;
  19. 	q = f(xa,xc,xb,ya,yc,yb);
  20. 	w = f(xd,xc,xb,yd,yc,yb);
  21. 	if (q * w < 0) {
  22. 		printf("не выпуклый");
  23. 		return 0;
  24. 	}
  25. 	int p,r;
  26. 	p = f(xa,xd,xc,ya,yd,yc);
  27. 	r = f(xb,xd,xc,yb,yd,yc);
  28. 	if (p * r < 0) {
  29. 		printf("не выпуклый");
  30. 		return 0;
  31. 	}
  32. 	int j,k;
  33. 	j = f(xb,xa,xd,yb,ya,yd);
  34. 	k = f(xc,xa,xd,yc,ya,yd);
  35. 	if (j * k < 0) {
  36. 		printf("не выпуклый");
  37. 		return 0;
  38. 	}
  39.  
  40. 	printf ("Выпуклый");
  41. 	return 0;
  42. }
Success #stdin #stdout 0s 3432KB
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-1 3 0 0 4 2 -1 -3
stdout
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не выпуклый
https://ideone.com/dsWBJc
задача про 4 точки
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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