题意描述
思路
AC代码
代码语言：javascript
复制#include<bits/stdc .h>
#define x first
#define y second
#define PB push_back
#define mst(x,a) memset(x,a,sizeof(x))
#define all(a) begin(a),end(a)
#define rep(x,l,u) for(ll x=l;x<u;x )
#define rrep(x,l,u) for(ll x=l;x>=u;x--)
#define sz(x) x.size()
#define IOS ios::sync_with_stdio(false);cin.tie(0);
using namespace std;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef pair<char,char> PCC;
typedef long long ll;
typedef pair<ll,ll> PLL;
const int N=3005;
const int M=1e5 10;
const int INF=0x3f3f3f3f;
const int MOD=1e9 7;
double a[N],f[N][N];
void solve(){
int n;cin>>n;
rep(i,1,n 1) cin>>a[i];
f[0][0]=1;
rep(i,1,n 1){
f[i][0]=f[i-1][0]*(1-a[i]);
rep(j,1,i 1){
f[i][j]=f[i-1][j-1]*a[i] f[i-1][j]*(1-a[i]);
}
}
double ans=0;
rep(i,0,n 1){
if(i>n-i) ans =f[n][i];
}
printf("%.9fn",ans);
}
int main(){
IOS;
//freopen("test.txt", "r", stdin);
//freopen("test.txt", "w", stdout);
//int t;cin>>t;
//while(t--)
solve();
return 0;
}
