standard deviation

#include <cmath> #include <cstdio> #include <vector> #include <iostream> #include <algorithm> #include <iomanip> using namespace std; double sum(vector<double> a) { double s = 0; for (int i = 0; i < a.size(); i++) { s += a[i]; } return s; } double sqsum(vector<double> a) { double s = 0; for (int i = 0; i < a.size(); i++) { s += pow(a[i],2); } return s; } int main() { /* Enter your code here. Read input from STDIN. Print output to STDOUT */ int N; cin >> N; vector<double> nums(N); for (int i = 0; i < nums.size(); i++) { cin >> nums[i]; } cout << fixed << setprecision(1) << pow(sqsum(nums) / N - pow(sum(nums) / N, 2), 0.5); return 0; }