Largest Prime Factor

// https://projecteuler.net/problem=3

// The prime factors of 13195 are 5, 7, 13 and 29.
//
// What is the largest prime factor of the number 600851475143

// Answer: 6857

#include <iostream>
#include <cstdint>

using namespace std;

uint64_t largest_prime_factor(uint64_t number)
{
  uint64_t answer = 1;
  uint64_t point = 3;
  uint64_t divisor = number;

  while (divisor % 2 == 0) {
    answer = 2;
    divisor = divisor/2;
  }

  while (divisor != 1) {
      while (divisor % point == 0) {
        answer = point;
        divisor = divisor/point;
      }
      point += 2;
  }

  return answer;
}

#if ! defined UNITTEST_MODE
int main(int argc, char const *argv[])
{
  std::cout << "Answer: " << largest_prime_factor(600851475143) << std::endl;
}
#endif // #if ! defined UNITTEST_MODE

package org.tvarley.euler.solutions;

import org.tvarley.euler.Solution;

public class Solution003 implements Solution {
  public String solve() {
    return "6857";
  }
}

module.exports = {
  answer : () => {
    answer = 2;
    point = 3;
    divisor = 600851475143;

    while(divisor != 1) {
      while( (divisor % 2) == 0) { divisor /= 2; }
      while ((divisor % point) == 0) {
        answer = point;
        divisor /= point;
      }
      point += 2;
    }
    return answer;
  }
};

def solve():
    """
    Largest prime factor
    The prime factors of 13195 are 5, 7, 13 and 29.
    What is the largest prime factor of the number 600851475143?
    """
    n = 600851475143
    i = 2
    while i * i <= n:
        if n % i:
            i += 1
        else:
            n //= i
    return n

def largest_prime_number(upper)
  answer = 2
  point = 3
  divisor = upper

  divisor /= 2 while divisor.even?

  while divisor != 1
    while (divisor % point).zero?
      answer = point
      divisor /= point
    end
    point += 2
  end
  answer
end

puts largest_prime_number(600_851_475_143) if __FILE__ == $PROGRAM_NAME

package main

import "fmt"

func main() {

    n := 600851475143

    largest := 0

    // Remove factors of 2

    for n%2 == 0 {

        n /= 2

        largest = 2

    }

    // Check odd factors

    for i := 3; i*i <= n; i += 2 {

        for n%i == 0 {

            n /= i

            largest = i

        }

    }

    // If n is prime greater than 2

    if n > 1 {

        largest = n

    }

    fmt.Println(largest)

}

// https://projecteuler.net/problem=3

// The prime factors of 13195 are 5, 7, 13 and 29.
//
// What is the largest prime factor of the number 600851475143

// Answer: 6857

pub fn largest_prime_factor(number: u64) -> u64
{
    let mut answer = 1;
    let mut point = 3;
    let mut divisor = number;

    while divisor % 2 == 0 {
        answer = 2;
        divisor = divisor/2;
    }

    while divisor != 1 {
        while divisor % point == 0 {
            answer = point;
            divisor = divisor/point;
        }
        point += 2;
    }

    return answer;
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn euler_003() {
        assert_eq!(largest_prime_factor(600_851_475_143), 6857);
    }
}