/*
*
* https://projecteuler.net/problem=5
*
* 2520 is the smallest number that can be divided by each of the numbers
* from 1 to 10 without any remainder.
*
* What is the smallest positive number that is evenly divisible by all of
* the numbers from 1 to 20?
*/
public static int FindSmallestNumberOfMultiplesUpTo(int limit)
{
var dict = new Dictionary <long, int>();
var range = new EulerRange(2, limit);
foreach (var item in range)
{
var primes = Helper.FindPrimeMultiples(item);
foreach (var prime in primes)
{
var cnt = primes.Count(x => x == prime);
if (!dict.ContainsKey(prime))
{
dict.Add(prime, 1);
}
if (dict[prime] < cnt)
{
dict[prime] = cnt;
}
}
}
var result = 1;
foreach (var item in dict)
{
result *= (int)Math.Pow(item.Key, item.Value);
}
return(result);
}
private int OptimizationAttempt1(int numDigits)
{
if (numDigits == 1)
{
return(9);
}
var upperLimit = (int)Math.Pow(10, numDigits) - 1;
var lowerLimit = upperLimit - (int)Math.Pow(10, numDigits - 1);
var range = new EulerRange(lowerLimit, upperLimit);
HashSet <int> numbers = new HashSet <int>();
//Get every multiple
foreach (var item in range)
{
range.Select(x => numbers.Add(item * x)).ToList();
}
foreach (var item in numbers.OrderByDescending(x => x))
{
if (NumberStringHelper.IsNumberPalindrome(item))
{
return(item);
}
}
return(-1);
}
private static void Taks1()
{
Console.WriteLine("Taks1:");
IRange fibonacci = new FibonacciRange(10);
Console.Write("Fibonacci:");
fibonacci.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
IRange euler = new EulerRange(10);
Console.Write("Euler:");
euler.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
}
private static void Task3()
{
Console.WriteLine("Taks3:");
IRange fibonacci = new FibonacciRange(10);
IRange euler = new EulerRange(10);
IRange rangeSumma = new RangeSumma(10, fibonacci, euler);
Console.Write("Fibonacci + Euler:");
rangeSumma.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
IRange rangeDifference = new RangeDifference(10, fibonacci, euler);
Console.Write("Fibonacci - Euler:");
rangeDifference.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
}
private static void Task2()
{
Console.WriteLine("Taks2:");
IRange fibonacci = new FibonacciRange(10);
IRange negativeFibonacciRange = new NegativeRange(fibonacci);
Console.Write("Negative Fibonacci:");
negativeFibonacciRange.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
IRange euler = new EulerRange(10);
IRange negativeEulerRange = new NegativeRange(euler);
Console.Write("Negative Euler:");
negativeEulerRange.Iterate(x => Console.Write(" {0}", x));
Console.WriteLine();
}
private int BruteForce(int numDigits)
{
var range = new EulerRange((int)Math.Pow(10, numDigits - 1), (int)Math.Pow(10, numDigits) - 1);
var numbers = new List <(int left, int right, int total)>();
//Get every multiple
foreach (var item in range)
{
numbers.AddRange(range.Select(x => (x, item, item * x)));
}
foreach (var item in numbers.OrderByDescending(x => x.total))
{
if (NumberStringHelper.IsNumberPalindrome(item.total))
{
return(item.total);
}
}
return(-1);
}