Submission #1025561

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
double f[110];
double r2=(double)1.0/2.0,r3=(double)1.0/3.0;
double c(int n,int m){
	double ret=1;
	for(int i=0;i<m;i++){
		ret*=n-i;
		ret/=m-i;
	}
	return ret;
}
double revc(int n,int m){return 1/c(n,m);}
double sol(int n){
	double ret=1;
	//if(n%3==0)ret+=f[n/3]*pow(r3,n)*c(n,n/3*2)*c(n/3*2,n/3);
	//if(n%2==0)ret+=f[n/2]*pow(r3*2,n-1)*revc(n-2,(n-2)/2);
	for(int i=1;n-i>=i;i++){
		ret+=f[i]*6*pow(r3,n)*c(n,i);
	}
	for(int i=1;n-2*i>=i;i++){
		//ret+=f[i]*pow(r3*2,i*2-2)*revc(i*2-2,i-1);
		ret+=f[i]*6*pow(r3,n)*c(n,2*i)*c(2*i,i);
	}
	for(int i=1;(n-i)/2>=i;i++){
		int nn=n-i;
		for(int j=i;nn-j>=i;j++){
			int k=nn-j;
			if(i==j&&j==k)continue;
			/*
			ret+=f[i]*pow(r3,i-1)
				*(r3*2)*pow(r3,j-1)
				*r3*pow(r3,k-1)
				*c(n,nn)
				*c(nn,j);
				*/
			ret+=f[i]*pow(r3,n)*c(n,nn)*c(nn,k);
		}
	}
	double tmp=0;
	if(n%3==0)tmp=pow(r3,n)*c(n,n/3*2)*c(n/3*2,n/3);
	ret/=1-(pow(r3,n-1)+tmp);
	return ret;
}
int main(){
	int n;
	scanf("%d",&n);
	f[1]=0;
	f[2]=1.5;
	for(int i=3;i<=n;i++)
		f[i]=sol(i);
	printf("%.6f\n",f[n]);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:47:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]

Judge Result