Submission #1695516

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define _rep(i,n) _repl(i,0,n)
#define rep(...) GET_MACRO(__VA_ARGS__, _repl, _rep)(__VA_ARGS__)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cout<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cout<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream &o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream &o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define double long double

typedef vector<vector<double>> mat;

// return A*B
mat mat_mul(const mat &A, const mat &B){
  int n=A.size(), m=B[0].size(), l=B.size();
  mat ret(n, vector<double>(m, 0));
  rep(i,n) rep(k,l) if(A[i][k]!=0) rep(j,m){
    (ret[i][j] += A[i][k] * B[k][j]);
  }
  return ret;
}

// A^p
mat mat_pow(const mat &A, long p){
  int n = A.size();
  mat tmp(A), ret(n, vector<double>(n,0));
  rep(i,n) ret[i][i] = 1;
  while(p>0){
    if(p&1) ret = mat_mul(tmp, ret);
    tmp = mat_mul(tmp, tmp);
    p /= 2.0;
  }
  return ret;
}

int main(){
  double p; long n;
  cin>>p>>n;

  mat m = {{1.0-p, p}, {p, 1.0-p}};
  m = mat_pow(m, n);

  printf("%.9Lf\n", m[0][1]);

  return 0;
}

Submission Info

Judge Result