????

????????????????????????????????????????? n ????????? S???????????????????????????????

??

?????????

??????????n ? S????????????????

??????? n ?????????????

??

?????????????????????

????

5 2333666 666 666 666 666 666

????

0.0000

????

???????????????????????????????????????????????????????????????????

[ s = \sqrt{\frac{1}{n} \sum_{i=1}^{n} \left(b_i - \frac{1}{n} \sum_{i=1}^{n} b_i \right)^2} ]

???( s ) ?????( b_i ) ?????????( n ) ?????????

???????????????????????????????????????????????????????????????

?????????????? ( \mu = \frac{S}{n} )?

???????????????

?????

??????????????????????

???????????????????????????????????????? cur_avg??? cur_avg ??????????

???????????????????????????????????

C++??

#include 
   
    using namespace std;typedef long long LL;int n;LL S;double ans = 0.0;double avg = 1.0 * S / n;LL *a = new LL[n];void work() {    scanf("%d %lld", &n, &S);    ans = 0.0;    avg = 1.0 * S / n;    LL *a = new LL[n];    for (int i = 0; i < n; ++i) {        scanf("%lld", &a[i]);    }    // ?????    double sum = 0.0;    for (int i = 0; i < n; ++i) {        double diff = a[i] - avg;        sum += diff * diff;    }    ans = sqrt(sum / n);    printf("%.4f", ans);}