题解 | #Balls#
Balls
https://ac.nowcoder.com/acm/problem/20709
Time: O(n)
Memory: O(1)
int n;
double s = 1.0 , p = 0.5;
//=================================
int main(){
n=read();
rep(i,1,n)
s = (s + 1.0) * p + s * (1.0 - p),p = 1.0 * s/(i+2.0);
printf("%.7lf",s);
return 0;
}
