Write a method called factorial that takes an integer parameter n and calculates

Question

Write a method called factorial that takes an integer parameter n and calculates n!, which is the product of the integers 1 through n. You can use either a for loop or try recursion to write this method.

Write another method called choose that takes two integer parameters n and k that calculates and returns the n th row k th term in pascal’s triangle. Calculators typically have this function available on them denoted either as nCk or as n k . It is used in combinatorics to count the number of ways we can choose k objects from a set of n unique objects, so assume 0 k n. The explicit formula makes use of your factorial method:

k!/k!(n-k)!

Explanation / Answer

Hi,

Here is the working code, i have added comments to help you understand.

import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
   public static void main (String[] args) throws java.lang.Exception
   {
       // your code goes here
       System.out.println(factorial(5));
       System.out.println(Combination(5,2));
   }
   static double Combination(int x, int y) {
if (y < 0 || y > x) return 0;
  
double a = 1.0, b = 1.0;
for (int i = 1; i <= y; i++) {
a = a*i; // denomiator
b =b* (x + 1 - i); //numerator
/* since n!/k!(n-k)! boils down to n*n-1..k times/k! */
}
return b / a;
}
   static int factorial(int number)// factorial
{
   int fact=1;
   for(int i=1;i<=number;i++){
fact=fact*i; //iteratively multiply from 1 to number
}   
return fact;
}
}

Thumbs up if this was helpful,otherwise let me know in comments. Good day

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