2-05. Calculate the mean variance of the Set Data (15) (zjupat mathematics)

Link: http://pat.zju.edu.cn/contests/ds/2-05

The design function calculates the mean variance of n given integers. If the average value of N numbers a [] is recorded as AVG, the formula for calculating the mean variance is:

Input format description:

The first line is a positive integer of N (<= 1st) and the second line is an integer of N.

Output format description:

The average variance of N numbers is output, which requires a fixed precision to output the 5 digits after the decimal point.

Sample input and output:

Serial number	Input	Output
1	106 3 7 1 4 8 2 9 11 5	3.03974
2	12	0.00000

The Code is as follows:

#include <cstdio>#include <cmath>int main(){    int a[10017];    double avg;    int n;    while(~scanf("%d",&n))    {        double sum = 0, ans = 0;        for(int i = 0; i < n; i++)        {            scanf("%d",&a[i]);            sum+=a[i];        }        avg = sum/(n*1.0);        sum = 0;        for(int i = 0; i < n; i++)        {            sum+=(a[i]-avg)*(a[i]-avg);        }        sum/=(n*1.0);        ans = sqrt(sum);        printf("%.5lf\n",ans);    }    return 0;}

2-05. Calculate the mean variance of the Set Data (15) (zjupat mathematics)