Project Euler | Problem 4 | Largest palindrome product

Problem Description :

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers?

Project Euler Problem 4

Concept :

A palindromic number or numeral palindrome is a number that remains the same when its digits are reversed. For example 99 is a palindrome but 89 is not.

Java Program :

package com.javamultiplex.projecteuler; /** * * @author Rohit Agarwal * @category Project Euler Problems * @problem Largest palindrome product * */ public class Problem4 { public static void main(String[] args) { int maxThreeDigit = 999; int minThreeDigit = 100; int multInteger = 0; // lowest multiple of 2 three digit numbers int max = 100 * 100; for (int i = maxThreeDigit; i >= minThreeDigit; i--) { for (int j = i; j >= minThreeDigit; j--) { multInteger = i * j; // Checking multiplication is palindrome or not if (isPalindrome(multInteger)) { if (multInteger > max) { max = multInteger; break; } } } } System.out.println("Largest palindrom made from the product of two 3-digit numbers is: " + max); } private static boolean isPalindrome(int multInteger) { boolean result = false; String multString = null; StringBuffer multStringBuffer = null; // Converting Integer to String multString = String.valueOf(multInteger); /* * Converting String to StringBuffer, We want to reverse the string * thats why we have to use StringBuffer. */ multStringBuffer = new StringBuffer(multString); if (multString.equals(multStringBuffer.reverse().toString())) { result = true; } else { result = false; } return result; } }

Output :

Output - Project Euler Problem 4

References :

https://projecteuler.net/problem=4

https://en.wikipedia.org/wiki/Palindromic_number

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html

https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuffer.html

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Tags : Project Euler Problem 4, Solution in Java, Mathematics problems, Largest palindrome product, if else statement, for loop, String, StringBuffer.

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