Tag Archives: rhino

Project Euler: Problems 1 – 5 in JavaScript

I’ve been wanting to check out Rhino for a while, and I’ve been particularly interested in seeing how it compares to Ruby in terms of speed. The results have been a little varied, and it’s a deeply flawed comparison. But it’s something.

These scripts are just ports of my ruby solutions. There are a few places where I had to roll my own JavaScript functions instead of baked in Ruby methods, but other than that it was nearly line by line translation.

Problem 1Ruby solution

Add all the natural numbers below one thousand that are multiples of 3 or 5.

var total = 0;

for(var i = 0; i < 1000; i++) {
  if(i % 3 == 0 || i % 5 == 0) {
    total += i;
  }
}

print(total);

Problem 2Ruby solution

Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million.

function fib(stack, n) {
  if(n == 0) {
    return 1;
  }
  if(n == 1) {
    return 2;
  }
  return stack[n - 1] + stack[n - 2];
}

var max   = 4000000;
var total = 0;
var stack = [];

for(var i = 0; i < max; i++) {
  stack[i] = fib(stack,i);
  if(stack[i] > max) {
    break;
  }
  if(stack[i] % 2 == 0) {
    total += stack[i]
  }
}

print(total);

Problem 3Ruby solution

Find the largest prime factor of a composite number.

function find_highest_prime_factor(n) {
  var max = Math.round(Math.sqrt(n));
  for(var i = max; i >= 2; i--) {
    if(n % i == 0 && find_highest_prime_factor(i) == 1) {
      return i;
    }
  }
  return 1;
}

var target = 600851475143;
print(find_highest_prime_factor(target));

Problem 4Ruby solution

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

function get_highest_palindrome(high, low) {
  var highest = 0;
  for(var i = high; i >= low; i--) {
	for(var j = high; j >= low; j--) {
      sum = i * j;
      if(sum <= highest) {
        break;
	  }
      if(is_palindrome(sum.toString())) {
        highest = max(highest, sum);
	  }
    }
  }
  return highest;
}

function reverse(string) {
  var array = string.split('').reverse();
  var out   = '';
  for(key in array) {
	out += array[key];
  }
  return out;
}

function max(a,b) {
  if(a > b) {
	return a;
  }
  return b;
}

function is_palindrome(string) {
  return string == reverse(string);
}

print(get_highest_palindrome(999, 100));

Problem 5 - Ruby solution

What is the smallest number that is evenly divisible by all of the numbers from 1 to 20?

function gcd(a,b) {
  var x = a;
  var y = b;
  var result;
  
  while (y != 0) {
	result = x % y;
    x      = y;
    y      = result;
  }
  return x;
}

function lcm(a,b) {
  return (a * b) / gcd(a, b);
}

var max = 20;
var min = 11;
var n   = min;

for(var i = min; i <= max; i++) {
  n = lcm(n,i);
}

print(n);