Codeforces Round #259 (Div. 1)??Little Pony and Expected Maximum_html/css_WEB-ITnose

Question connection

Question meaning:
Input n, m, representing an n-sided die (the value on the surface is 1-n), throw m times, find the expectation of the maximum value (1?≤?m,?n?≤?105).

Analysis:
Assuming that the current maximum value is Max, then the corresponding probability is : sigma (C(m, k) * ((1 / n) ^ k ) * (((Max - 1) / n) ^ (m - k)) ), (1 <= k <= n) ; Simplify to get: sigma (C(m, k) * ((1 / n) ^ k ) * (((Max - 1) / n) ^ (m - k)) ) - ((Max - 1 ) / n) ^ m, (0 <= k <= n); Max ^ m can be obtained from the binomial in the first half, then the simplified result is Max ^ m - (Max - 1) ^ m. Finally, multiply it by Max to get the expectation. Max can use enumeration
After sighing, I found that the efficiency of pow function and fast power are the same. .

int main (){    int n, m;    while (~RII(n, m))    {        double ans = 0;        FE(Max, 1, n)        {            ans += Max * (pow((double)Max / n, m) - pow((Max - 1.0) / n, m));        }        printf("%.10f\n", ans);    }    return 0;}