Day 1: Standard Deviation HackerRank Solution

Day 1: Standard Deviation HackerRank Solution
Source : https://www.hackerrank.com/challenges/s10-standard-deviation

Objective
In this challenge, we practice calculating standard deviation. Check out the Tutorial tab for learning materials and an instructional video!

Task
Given an array, , of integers, calculate and print the standard deviation. Your answer should be in decimal form, rounded to a scale of decimal place (i.e., format). An error margin of will be tolerated for the standard deviation.

Input Format

The first line contains an integer, , denoting the number of elements in the array.
The second line contains space-separated integers describing the respective elements of the array.

Constraints

• , where is the element of array .

Output Format

Print the standard deviation on a new line, rounded to a scale of decimal place (i.e., format).

Sample Input

510 40 30 50 20

Sample Output

14.1

Explanation

First, we find the mean:

Next, we calculate the squared distance from the mean, , for each :

Now we can compute , so:

Once rounded to a scale of decimal place, our result is .

Source : https://www.hackerrank.com/challenges/s10-standard-deviation

Solution

	// github.com/RodneyShag
	import java.util.Scanner;
	public class Solution {
	public static void main(String[] args) {
	/* Save input */
	Scanner scan = new Scanner(System.in);
	int size = scan.nextInt();
	int [] array = new int[size];
	for (int i = 0; i < size; i++) {
	array[i] = scan.nextInt();
	}
	scan.close();
	System.out.format("%.1f", standardDeviation(array));
	}
	public static double getMean(int [] array) {
	int sum = 0;
	for (int x : array) {
	sum += x;
	}
	return (double) sum / array.length;
	}
	public static double standardDeviation(int [] array) {
	double mean = getMean(array);
	double sum = 0;
	for (int x : array) {
	sum += Math.pow(x - mean, 2);
	}
	double variance = sum / array.length;
	return Math.sqrt(variance);
	}
	}