Day 5: Poisson Distribution I HackerRank Solution

Day 5: Poisson Distribution I HackerRank Solution
Source : https://www.hackerrank.com/challenges/s10-poisson-distribution-1

Objective
In this challenge, we learn about Poisson distributions. Check out the Tutorial tab for learning materials!

Task
A random variable, , follows Poisson distribution with mean of . Find the probability with which the random variable is equal to .

Input Format

The first line contains 's mean. The second line contains the value we want the probability for:

2.55

If you do not wish to read this information from stdin, you can hard-code it into your program.

Output Format

Print a single line denoting the answer, rounded to a scale of decimal places (i.e., format).

Source : https://www.hackerrank.com/challenges/s10-poisson-distribution-1

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);
	double lambda = scan.nextDouble();
	int k = scan.nextInt();
	scan.close();
	System.out.println(poisson(k, lambda));
	}
	private static double poisson(int k, double lambda) {
	return (Math.pow(lambda, k) * Math.pow(Math.E, -1 * lambda)) / factorial(k);
	}
	private static Long factorial(int n) {
	if (n < 0) {
	return null;
	}
	long result = 1;
	while (n > 0) {
	result *= n--;
	}
	return result;
	}
	}