Submission #60710589

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Source Code Expand

#include<bits/stdc++.h>
#define LL long long
#define ull unsigned long long
#define lc(p) ((p)*2)
#define rc(p) ((p)*2+1)
#define mkpr make_pair
#define fir first
#define sec second
using namespace std;
inline LL read() {
	LL x=0;
	bool t=0;
	char ch=getchar();
	while(ch<'0'||ch>'9')t|=(ch=='-'),ch=getchar();
	while(ch>='0'&&ch<='9')x=x*10+(ch^48),ch=getchar();
	return t?-x:x;
}
const int N=5005;
int n,m,a[N];
double p[N];
double f[N][N],g[N];
int main() {
	cin>>n>>m;
	for(int i=1; i<=n; i++) {
		cin>>a[i];
		p[i]=1.0*a[i]/100;
	}
	f[0][0]=1;
	for(int i=1; i<=n; i++) {
		f[i][0]=f[i-1][0]*(1-p[i]);
		for(int j=1; j<=i; j++) {
			f[i][j]=f[i-1][j-1]*p[i]+f[i-1][j]*(1-p[i]);
		}
	}
	g[0]=0;
	for(int i=1;i<=m;i++){
		g[i]=1;
		for(int j=1;j<=n;j++){
			g[i]+=g[max(0,i-j)]*f[n][j];
		}
		g[i]/=(1-f[n][0]);
	}
	printf("%.10lf",g[m]);
	return 0;
}
/*
f[i][j]=f[i-1][j-1]*p[i]+f[i-1][j]*(1-p[i])

g[i]=1+sum(g[i-j]*f[n][j])+g[i]*f[n][0] (1<=j<=n)

g[i]*(1-f[n][0])=1+sum(g[i-j]*f[n][j]) (1<=j<=n)
*/

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