Submission #4483996

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Source Code Expand

#include "bits/stdc++.h"
#include <cmath>
#define ALL(x) x.begin(), x.end()
#define LEN(x) (int)x.size()
#define iostreamBooster() do{ cin.tie(nullptr); ios_base::sync_with_stdio(false); }while(0)
using namespace std;
typedef int64_t i64;
typedef pair<int,int> pii;
template<class A, class B>inline bool chmax(A &a, const B &b){return b>a ? a=b,1 : 0;}
template<class A, class B>inline bool chmin(A &a, const B &b){return b<a ? a=b,1 : 0;}
constexpr int INF = 0x3f3f3f3f;

signed main()
{
  int R, N, M;
  double len[200100] {};

  cin >> R >> N >> M;
  const double P = (double)2*R / (double)N;

  for (int l = 1, r = N-1; l <= r; ++l, --r) {
    const double w = ((double)R - P*l);
    len[l] = len[r] = 2 * sqrt((double)R*R - w*w);
  }

  auto getlen = [&](int i) { return (i < 0 || i >= N)?  0.0 : len[i]; };

  double ans = 0;
  for (int i = 1; i < (N+M); ++i) {
    ans += fmax(getlen(i), getlen(i-M));
  }

  cout << fixed << setprecision(10) << ans << endl;

  return 0;
}

Submission Info

Judge Result