code4sk/c/sourcecode/朱森森带领的奇妙冒险/2022-2023第二学期单开班第2次月考/7-2 求集合数据的均方差.cpp

/*
7-2 ?????????
?? 10
?? ???
?? ????
????? N ???????????? N ?? A[ ] ?????? Avg,?????????: 
[(A 
1
?
 -Avg) 
2
 +(A 
2
?
 -Avg) 
2
 +?+(A 
N
?
 -Avg) 
2
 ]/N
?
 ?

????:
??????????????? N(=10 
4
 ),?????? N ????????????? 1000,??????????

????:
???N??????,????????????5??

???? 1:
10
6 3 7 1 4 8 2 9 11 5
???? 1:
3.03974
???? 2:
1
2
???? 2:
0.00000
*/

#include<stdio.h>
#include<math.h>
int main(){
	int N,i,num,sum=0;
	double final,avg,sum2=0;
	scanf("%d",&N);
	int a[N];
	for(i=0;i<N;i++){
		scanf("%d",&a[i]);
		sum+=a[i];
	}
	avg=1.0*sum/N;
	for(i=0;i<N;i++){
		sum2+=pow(a[i]-avg,2);
	}
	final=sqrt(sum2/N);
	printf("%.5lf",final);
	return 0;
}