//-----
//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.
//-----
public static int FindLargestPalindrome(int n)
{
int result = 0;
int last = 1;
switch (n)
{
case 3:
{
last = 999; break;
}
default:
break;
}
for (int i = 100; i <= last; i++)
{
int number3 = 0;
for (int k = i; k <= last; k++)
{
number3 = i * k;
if (Problem4.ItPalindromicNumber(number3))
{
if (number3 > result)
{
result = number3;
}
}
}
}
return(result);
}
static void Main(string[] args)
{
Console.WriteLine("Enter the number of problem.");
Console.Write("Problem number: ");
int problemNumber = Convert.ToInt32(Console.ReadLine());
switch (problemNumber)
{
case 1:
{
Console.WriteLine("Find the sum of all the multiples of 3 or 5 below 1000.");
Console.WriteLine();
Console.WriteLine("Enter the number between 1 and 1000.");
Console.Write("Yuor number: ");
int a = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("The Sum of all the multiples of 3 or 5 below {0}: {1}.", a, Problem1.SumOfDivision3and5(a));
break;
}
case 2:
{
Console.WriteLine("By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.");
Console.WriteLine();
Console.WriteLine("Enter the number greater than 2.");
Console.Write("Yuor number: ");
int a = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("The sum of the even-valued Fibonacci nambers below {0}: {1}.", a, Problem2.SumOfEvenFibonacciNumbers(a));
break;
}
case 3:
{
Console.WriteLine("What is the largest prime factor of the number n ?");
Console.WriteLine();
Console.WriteLine("Enter the number greater than 2.");
Console.Write("Yuor number: ");
long a = Convert.ToInt64(Console.ReadLine());
List <long> PrameFactors = new List <long>();
PrameFactors = Problem3.FindPrimeNumbers(a);
Console.WriteLine("The primes factors of the number {0}:", a);
Console.WriteLine();
int lenght = PrameFactors.Count;
if (lenght == 1)
{
Console.WriteLine("{0}", PrameFactors[0]);
}
else
{
for (int i = 0; i < lenght; i++)
{
if (i == 0)
{
Console.Write("{0}, ", PrameFactors[i]);
}
else if (i == (lenght - 1))
{
Console.WriteLine("{0}.", PrameFactors[i]);
}
else
{
Console.Write("{0}, ", PrameFactors[i]);
}
}
}
Console.WriteLine();
Console.WriteLine("The largest prime factor of the number {0}: {1}.",
a, Problem3.FindMaxNumber(PrameFactors));
break;
}
case 4:
{
Console.WriteLine("Find the largest palindrome made from the product of two 3 - digit numbers.");
Console.WriteLine();
Console.WriteLine("Enter the number 3.");
Console.Write("Yuor number: ");
int n = Convert.ToInt32(Console.ReadLine());
int largestpalindrome = Problem4.FindLargestPalindrome(n);
Console.WriteLine("The largest palindrome made from the product of two 3 - digit numbers is {0}.", largestpalindrome);
break;
}
case 6:
{
Console.WriteLine("Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.");
Console.WriteLine();
Console.WriteLine("Enter the number greater than 1.");
Console.Write("Yuor number: ");
int n = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("The difference between the sum of the squares of the first one hundred natural numbers and the square of the sum: {0}.",
Problem6.SquereOfSumNaturalNumbers(n) - Problem6.SumOfSquaresNaturalNumbers(n));
break;
}
case 7:
{
Console.WriteLine("What is the 10 001st prime number?");
Console.WriteLine();
Console.WriteLine("Enter the number greater than 1.");
Console.Write("Yuor number: ");
int n = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("The {0}st prime number: {1}.", n, Problem7.FindPrimeNumberN(n));
break;
}
default:
break;
}
}