标签：from friend each upper desc dash script appear div
Description
Twilight Sparkle was playing Ludo with her friends Rainbow Dash, Apple Jack and Flutter Shy. But she kept losing. Having returned to the castle, Twilight Sparkle became interested in the dice that were used in the game.
The dice has m faces: the first face of the dice contains a dot, the second one contains two dots, and so on, the
m-th face contains
m dots. Twilight Sparkle is sure that when the dice is tossed, each face appears with probability
. Also she knows that each toss is independent from others. Help her to calculate the expected maximum number of dots she could get after
tossing the dice n times.
Input
A single line contains two integers m and n (1?≤?m,?n?≤?105).
Output
Output a single real number corresponding to the expected maximum. The answer will be considered correct if its relative or absolute error doesn‘t exceed 10??-?4.
Sample Input
6 1
3.500000000000
6 3
4.958333333333
2 2
1.750000000000
Hint
Consider the third test example. If you‘ve made two tosses:
The probability of each outcome is 0.25, that is expectation equals to:
You can read about expectation using the following link: http://en.wikipedia.org/wiki/Expected_value
#include<iostream> //此题要先转化成概率形式,否则会爆double的
#include<cstdio>
#include<cmath>
#include<cstring>
#include<queue>
#include<algorithm>
#define INF 0x3f3f3f3f
using namespace std;
int a[200010];
int main()
{
int n, m;
while(~scanf("%d%d", &m, &n))
{
double ans = 0;
for (int i = 1; i < m; i++)
ans += pow((double)i / m, n);
printf("%.12lf\n", (double) m - ans);
}
}
/*
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<queue>
#include<algorithm>
#define INF 0x3f3f3f3f
using namespace std;
int a[200010];
int main()
{
int n,m;
while(~scanf("%d%d",&m,&n))
{
double sum1=0,sum2=0,sum=0;
for(int i=1;i<=m;i++)
{
sum2=pow(i*1.0/m,n);
sum+=i*(sum2-sum1);
sum1=sum2;
}
double ss=1.0*sum;
printf("%.12lf\n",ss);
}
}
*/标签：from friend each upper desc dash script appear div
原文地址：http://www.cnblogs.com/brucemengbm/p/6890690.html
