fork download
copy 
  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. #define ll long long
  5. #define sd(x) scanf("%d", &(x))
  6. #define pii pair<int, int>
  7. #define F first
  8. #define S second
  9. #define all(c) ((c).begin()), ((c).end())
  10. #define sz(x) ((int)(x).size())
  11. #define ld long double
  12.  
  13. template<class T,class U>
  14. ostream& operator<<(ostream& os,const pair<T,U>& p){
  15. 	os<<"("<<p.first<<", "<<p.second<<")";
  16. 	return os;
  17. }
  18.  
  19. template<class T>
  20. ostream& operator <<(ostream& os,const vector<T>& v){
  21. 	os<<"{";
  22. 	for(int i = 0;i < (int)v.size(); i++){
  23. 		if(i)os<<", ";
  24. 		os<<v[i];
  25. 	}
  26. 	os<<"}";
  27. 	return os;
  28. }
  29.  
  30. #ifdef LOCAL
  31. #define cerr cout
  32. #else
  33. #endif
  34.  
  35. #define TRACE
  36.  
  37. #ifdef TRACE
  38. #define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
  39. template <typename Arg1>
  40. void __f(const char* name, Arg1&& arg1){
  41. 	cerr << name << " : " << arg1 << std::endl;
  42. }
  43. template <typename Arg1, typename... Args>
  44. void __f(const char* names, Arg1&& arg1, Args&&... args){
  45. 	const char* comma = strchr(names + 1, ',');cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
  46. }
  47. #else
  48. #define trace(...)
  49. #endif
  50.  
  51. struct PT{
  52.     ll a, b;
  53.     PT(){}
  54.     PT(ll _a, ll _b) : a(_a), b(_b){};
  55.     PT operator - (const PT & p) const{
  56.         return PT(a - p.a, b - p.b);
  57.     }
  58.     PT operator + (const PT & p) const{
  59.         return PT(a + p.a, b + p.b);
  60.     }
  61.  
  62.     ll operator * (const PT & p) const{
  63.         return (a * p.b - b * p.a);
  64.     }
  65. };
  66.  
  67. const int N = 100005;
  68. PT P[N];
  69. int main(){
  70.     int n; sd(n);
  71.     for(int i = 0; i < n; i++){
  72.         scanf("%lld", &P[i].a),scanf("%lld", &P[i].b);
  73.         assert(max(abs(P[i].a), abs(P[i].b)) <= 1e7);
  74.     }
  75.     ll areaP = 0, area = 0;
  76.  
  77.     for(int i = 0; i < n; i++){
  78.         PT p = P[i] - P[(i + n - 1) % n], q = P[(i + 1) % n] - P[i];
  79.         ll z = p * q;
  80.         assert(z > 0);
  81.         area += abs(p * q);
  82.         areaP += p * P[i];
  83.     }
  84.     areaP = abs(areaP);
  85.     printf("%.10lf\n", (4 * areaP - area) / 8.);
  86. }
Runtime error #stdin #stdout #stderr 0s 4516KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Standard output is empty
stderr
copy 
prog: prog.cpp:80: int main(): Assertion `z > 0' failed.
https://ideone.com/evvtFf
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!