HackerRank Contest - Project Euler - Largest Prime Factor
Solution⌗
- Find all the factors of the given number by iterating from 1 to square root of the number.
- Sort all the factors in descending order and iterate to check if a factor is prime.
/* Solution to HackerRank: Largest Prime Factor
* URL: https://www.hackerrank.com/contests/projecteuler/challenges/euler003
*/
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int t = in.nextInt();
for(int a0 = 0; a0 < t; a0++){
long n = in.nextLong();
// get all the factors and sort is descending order
List<Long> factors = getFactors(n);
Collections.sort(factors, Collections.reverseOrder());
for(Long factor: factors){
if(isPrime(factor)){
System.out.println(factor);
break;
}
}
}
}
static List<Long> getFactors(long n){
List<Long> factors = new ArrayList<>();
for(long i = 1; i <= Math.sqrt(n); i++){
if(n%i == 0){
factors.add(i);
factors.add(n/i);
}
}
return factors;
}
static boolean isPrime(long n){
if(n%2 == 0){
return false;
}
for(long i = 3; i <= Math.sqrt(n); i+=2){
if(n%i == 0){
return false;
}
}
return true;
}
}
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