Submission #188235

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Source Code Expand

#include <iostream>
#include <iomanip>
#include <sstream>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
#include <numeric>
#include <utility>
#include <cmath>

using namespace std; using namespace placeholders;

using LL = long long;
using ULL = unsigned long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VS = vector<string>;
using SS = stringstream;
using PII = pair<int,int>;
using VPII = vector< pair<int,int> >;
template < typename T = int > using VT = vector<T>;
template < typename T = int > using VVT = VT< VT<T> >;
template < typename T = int > using LIM = numeric_limits<T>;

template < typename T > inline T fromString( const string &s ){ T res; istringstream iss( s ); iss >> res; return res; };
template < typename T > inline string toString( const T &a ){ ostringstream oss; oss << a; return oss.str(); };

#define REP( i, m, n ) for ( int i = (int)( m ); i < (int)( n ); ++i )
#define FOR( e, c ) for ( auto &e : c )
#define ALL( c ) (c).begin(), (c).end()
#define AALL( a, t ) (t*)a, (t*)a + sizeof( a ) / sizeof( t )
#define DRANGE( c, p ) (c).begin(), (c).begin() + p, (c).end()

#define PB( n ) push_back( n )
#define MP( a, b ) make_pair( ( a ), ( b ) )
#define EXIST( c, e ) ( (c).find( e ) != (c).end() )

#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

constexpr int dx[] = { 0, 1, 0, -1 };
constexpr int dy[] = { 1, 0, -1, 0 };

int main()
{
	cin.tie( 0 );
	ios::sync_with_stdio( false );

	int n, d, x, y;
	cin >> n >> d >> x >> y;

	if ( x % d || y % d )
	{
		cout << 0.0 << endl;
		return 0;
	}

	x /= d;
	y /= d;

	VT< map<PII,double> > dp( n + 1 );
	dp[0][ MP( 0, 0 ) ] = 1;

	REP( i, 0, n )
	{
		FOR( a, dp[i] )
		{
			const PII &pos = a.fst;
			const double p = a.snd;

			if ( n - i < abs( pos.fst - x ) + abs( pos.snd - y ) )
			{
				continue;
			}

			REP( d, 0, 4 )
			{
				dp[ i + 1 ][ MP( pos.fst + dx[d], pos.snd + dy[d] ) ] += p / 4;
			}
		}
	}

	cout << setprecision( 12 ) << fixed << dp[n][ MP( x, y ) ] << endl;



	return 0;
}

Submission Info

Judge Result