Artifact 86bec40a9221e580f7322c86d2996ef4d15640e7
#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <functional>
#include <complex>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <tuple>
using namespace std;
typedef long long LL;
typedef complex<double> CMP;
int K;
static const unsigned MODVAL = 1000000007;
struct mint
{
unsigned val;
mint():val(0){}
mint(int x):val(x%MODVAL) {}
mint(unsigned x):val(x%MODVAL) {}
mint(LL x):val(x%MODVAL) {}
};
mint& operator+=(mint& x, mint y) { return x = x.val+y.val; }
mint& operator-=(mint& x, mint y) { return x = x.val-y.val+MODVAL; }
mint& operator*=(mint& x, mint y) { return x = LL(x.val)*y.val; }
mint operator+(mint x, mint y) { return x+=y; }
mint operator-(mint x, mint y) { return x-=y; }
mint operator*(mint x, mint y) { return x*=y; }
mint POW(mint x, LL e) { mint v=1; for(;e;x*=x,e>>=1) if(e&1) v*=x; return v; }
mint& operator/=(mint& x, mint y) { return x *= POW(y, MODVAL-2); }
mint operator/(mint x, mint y) { return x/=y; }
vector<mint> solve(int N, vector<mint> q)
{
if(N == 1)
return vector<mint>(1, mint(1));
vector<mint> p(N);
for(int s=0; s<N; ++s) {
int d = ((N+1-K)%N+N)%N;
if(s == d) {
p[s] = 2 * (d<N-1 ? q[d]/2 : mint(0));
break;
}
}
for(int s=0; s<N; ++s) {
int d = ((N+1-K)%N+N)%N;
if(s != d) {
p[s] = p[d]/2 + (d<N-1 ? q[d]/2 : mint(0));
}
}
return p;
}
class BearCircleGame { public:
int winProbability(int n, int k)
{
K = k;
vector<mint> p;
for(int nn=1; nn<=n; ++nn)
p = solve(nn, p);
return p[0].val;
}
};
// BEGIN CUT HERE
#include <ctime>
double start_time; string timer()
{ ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
{ os << "{ ";
for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
void verify_case(const int& Expected, const int& Received) {
bool ok = (Expected == Received);
if(ok) cerr << "PASSED" << timer() << endl; else { cerr << "FAILED" << timer() << endl;
cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
#define END verify_case(_, BearCircleGame().winProbability(n, k));}
int main(){
CASE(0)
int n = 2;
int k = 1;
int _ = 333333336;
END
CASE(1)
int n = 2;
int k = 2;
int _ = 1;
END
CASE(2)
int n = 3;
int k = 2;
int _ = 142857144;
END
CASE(3)
int n = 3;
int k = 1;
int _ = 238095240;
END
CASE(4)
int n = 4;
int k = 4;
int _ = 142857144;
END
CASE(5)
int n = 5;
int k = 1000000000;
int _ = 142857144;
END
CASE(6)
int n = 2000;
int k = 123;
int _ = 429232785;
END
CASE(7)
int n = 1987;
int k = 987654321;
int _ = 623410299;
END
/*
CASE(8)
int n = ;
int k = ;
int _ = ;
END
CASE(9)
int n = ;
int k = ;
int _ = ;
END
*/
}
// END CUT HERE