How To Uncovering Largest Prime Number Component Of A Break Inwards Coffee - Programming Kata

One of the mutual programming kata to larn coding is write a plan to discovery the largest prime cistron of a number. Like whatsoever other programming problem, you lot demand to cook the logic to solve this problem. Before solving the problem, let's revise the concept of lay out theory. Prime factors of a positive integer are the prime numbers that carve upwardly the lay out just i.e. without whatsoever remainder, in addition to prime factorization is the procedure of finding all prime numbers when multiply together brand master copy number.  A positive integer tin own got multiple prime factors, our challenge is to discovery the largest prime cistron of a number. For example, half dozen has ii prime factors 2 in addition to 3, your plan should provide 3, because that's the largest prime factors. In ane of earlier problem, nosotros own got learned how to discovery prime cistron of a lay out inwards Java in addition to nosotros volition piece of work the like logic here, simply instead of returning a listing of prime factors nosotros volition alone provide the largest prime factor.

Java Program to Find Largest Prime Factor of an Integer

Problem : Write a plan to discovery the largest prime cistron of a positive integer inwards Java. If nosotros top xv to your program, it should provide 5, in addition to if nosotros top half dozen to your plan it should provide 3.

Solution : As nosotros learned a lay out is called prime cistron if it is prime lay out in addition to it tin carve upwardly the lay out exactly. Another belongings of prime cistron is that if nosotros choke on dividing the lay out past times prime cistron hence it volition either fully carve upwardly the lay out or create unopen to other prime cistron e.g. if nosotros demand to discovery the prime factors of xvi hence starting from 2 if choke on dividing, eventually dividend acquire 1, hence 2 is the alone prime cistron of 16. On other paw if demand to discovery prime cistron of 15, hence nosotros showtime endeavor to carve upwardly it past times 2, simply since its non divisible past times 2, nosotros motility to adjacent lay out which is 3. Since three tin carve upwardly 15, it produces unopen to other prime lay out 5, right away five is non divisible past times anything other than 5, hence three in addition to five acquire prime cistron of 15.

Algorithm : In our program, nosotros own got used the same logic. We start amongst 2, the smallest prime lay out in addition to endeavor to carve upwardly the number, if lay out is divisible hence nosotros choke on dividing it past times same lay out until its non divisible whatsoever more. Now nosotros motility to adjacent number, the largest lay out which is able to fully carve upwardly the input is our largest prime factor. This would last to a greater extent than clear when you lot come across the actual program.

import java.util.Random; import java.util.Scanner;  /** * Java plan to discovery in addition to impress largest prime cistron of an integer number. for * instance lay out half dozen has ii prime factors 2 in addition to 3, simply three is the largest prime * cistron of 6. input xv output five * * @author Javin Paul */ public class LargetPrimeFactor{      public static void main(String args[]) {          System.out.printf("Largest prime cistron of lay out '%d' is %d %n",                 6, largestPrimeFactor(6));         System.out.printf("highest prime cistron of lay out '%d' is %d %n",                 15, largestPrimeFactor(15));         System.out.printf("Biggest prime cistron of lay out '%d' is %d %n",                 392832, largestPrimeFactor(392832));         System.out.printf("Largest prime cistron of lay out '%d' is %d %n",                 1787866, largestPrimeFactor(1787866));     }      /**      * @return largest prime cistron of a lay out      */     public static int largestPrimeFactor(long number) {         int i;         long copyOfInput = number;          for (i = 2; i <= copyOfInput; i++) {             if (copyOfInput % i == 0) {                 copyOfInput /= i;                 i--;             }         }          return i;     }  }  Output: Largest prime cistron of lay out '6' is 3 highest prime cistron of lay out '15' is 5 Biggest prime cistron of lay out '392832' is 31 Largest prime cistron of lay out '1787866' is 893933

You tin come across from output that our plan is working properly, for half dozen the largest prime cistron is three in addition to for xv its 5. Here is our unit of measurement seek out to depository fiscal establishment tally brace of to a greater extent than numbers :

import static org.junit.Assert.assertEquals;  import org.junit.Test;  public class LargestPrimeFactorTest {              @Test     public void testLargestPrimeFactors(){         assertEquals(2, HelloWorld.largestPrimeFactor(2));         assertEquals(3, HelloWorld.largestPrimeFactor(6));         assertEquals(5, HelloWorld.largestPrimeFactor(15));         assertEquals(7, HelloWorld.largestPrimeFactor(147));         assertEquals(17, HelloWorld.largestPrimeFactor(17));         assertEquals(31, HelloWorld.largestPrimeFactor(392832));         assertEquals(893933, HelloWorld.largestPrimeFactor(1787866));     }          }

in addition to hither is the seek out result, you lot tin come across the seek out passed successfully.

One matter to banknote hither is that nosotros are non treatment invalid input hither e.g. 0, 1 or negative number, which nosotros should if this inquiry is asked on Interview. You tin throw IllegalArgumentException for those inputs which are non valid every bit per occupation specification. Similarly, you lot too demand to include unit of measurement seek out to depository fiscal establishment tally those invalid inputs. I acquire out that business for you lot every bit practice.


That's all nearly how to discovery largest prime cistron of a lay out inwards Java. This is a actually expert exercise to larn coding when you lot are starting amongst Java or Python or whatsoever other programming language. This sort of occupation volition help to cook your programming logic in addition to amend your coding skill. Believe me, its non slowly to convert a existent life algorithm into plan without practice. You must solve unopen to basic coding occupation based upon String, array in addition to recursion to acquire agree of coding. I own got shared many such exercise inwards this blog, if you lot are interested you lot tin too accept a await at next listing of occupation :

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• How to calculate factorial using recursion inwards Java? (Click here for solution)

Further Learning
The Coding Interview Bootcamp: Algorithms + Data Structures
Data Structures in addition to Algorithms: Deep Dive Using Java
Algorithms in addition to Data Structures - Part 1 in addition to 2

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