Submission #188067

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Source Code Expand

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cassert>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <functional>
#include <iostream>
#include <map>
#include <set>
using namespace std;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
typedef long long ll;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
 
 
int main()
{
	int n,d,x,y;
	cin >> n >> d >> x >> y;
	if(x%d != 0 || y%d != 0)
	{
		puts("0.0");
		return 0;
	}
	int amb = x/d;
	int cmd = y/d;
	if( ((amb+cmd)%2+2)%2 != n%2)
	{
		puts("0.0");
		return 0;
	}
	double res = 0.0;
	for(int i=0;i<=n;i++)
	{
		if(i-amb < 0) continue;
		int cpd = n-(i+i-amb);
		if( (cpd-cmd)%2 != 0) continue;
		if( (cpd+cmd)/2 < 0) continue;
		if( (cpd-cmd)/2 < 0) continue;
		int a = i;
		int b = i-amb;
		int c = (cpd+cmd)/2;
		int d = (cpd-cmd)/2;
		double tot = 1.0;
		int nxt = 1;
		for(int i=1;i<=n;i++)
		{
			tot/=4.0;
			while(tot <= 1e-50 && nxt<=n)
			{
				tot*=nxt;
				nxt++;
			}
		}
		for(int i=1;i<=a;i++)
		{
			tot/=i;
			while(tot <= 1e-50 && nxt<=n)
			{
				tot*=nxt;
				nxt++;
			}
		}
		for(int i=1;i<=b;i++)
		{
			tot/=i;
			while(tot <= 1e-50 && nxt<=n)
			{
				tot*=nxt;
				nxt++;
			}
		}
		for(int i=1;i<=c;i++)
		{
			tot/=i;
			while(tot <= 1e-50 && nxt<=n)
			{
				tot*=nxt;
				nxt++;
			}
		}
		for(int i=1;i<=d;i++)
		{
			tot/=i;
			while(tot <= 1e-50 && nxt<=n)
			{
				tot*=nxt;
				nxt++;
			}
		}
		while(nxt<=n)
		{
			tot*=nxt;
			nxt++;
		}
		res += tot;
	}
	printf("%.10f\n",res);
}

Submission Info

Judge Result