[概率DP] Codeforces 453A Little Pony and Expected Maximum

比较简单的概率题

f(k)=(k/n)^m-f(k-1)

#include<cstdio>  #include<cstdlib>#include<algorithm>  using namespace std;  int n,m;  inline double Pow(double a,int b){  double ret=1;  for (;b;b>>=1,a*=a)    if (b&1)      ret*=a;  return ret;}  int main(){    scanf("%d%d",&n,&m);    double ans=0,last=0;  for (int k=1;k<=n;k++){      double t=(double)k/n;      t=Pow(t,m);      ans+=(t-last)*k;      last=t;    }    printf("%.6lf\n",ans);  return 0;  }