Project Euler #5 : Smallest multiple

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?

Solution

using System; using System.Collections.Generic; using System.IO; class Solution {     static void Main(String[] args) {          int testCases = Convert.ToInt32(Console.ReadLine());             int[] numbers = new int[testCases];             for (int i = 0; i < testCases; i++)             {                 numbers[i] = Convert.ToInt32(Console.ReadLine());             }             foreach (int number in numbers)             {                 long product = 1;                 for (int i = 2; i <= number; i++)                 {                     if(IsPrime(i))                     {                         int temp = i;                         for(int j=2;j<=number;j++)                         {                             if(Math.Pow(Convert.ToDouble(i),Convert.ToDouble(j))>number)                             {                                 break;                             }                             else                             {                                 temp = Convert.ToInt32(Math.Pow(Convert.ToDouble(i), Convert.ToDouble(j)));                             }                         }                         product = product * temp;                     }                 }                 Console.WriteLine(product);             }     }     public static bool IsPrime(int number)         {             if (number == 2 || number == 3)                 return true;             else             {                 bool flag = true;                 for (int i = 2; i <= Math.Sqrt(number); i++)                 {                     if (number % i == 0)                     {                         flag = false;                         break;                     }                 }                 return flag;             }         } }

Project Euler #4 : Largest palindrome product

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

Solution

using System; using System.Collections.Generic; using System.IO; class Solution {     static void Main(String[] args) {          int testCases = Convert.ToInt32(Console.ReadLine());             List<int> numbers = new List<int>();             for (int k = 0; k < testCases; k++)             {                 numbers.Add(Convert.ToInt32(Console.ReadLine()));             }             foreach (int number in numbers)             {                 Console.WriteLine(FindLargestNumber(number));             }     }     public static int FindLargestNumber(int number)         {             for (int x = 9; x >= 0; --x)             {                 int a = x * 100001;                 for (int y = 9; y >= 0; --y)                 {                     int b = a + y * 10010;                     for (int z = 9; z >= 0; --z)                     {                         int n = b + z * 1100;                         if (n < number)                         {                             for (int i = 990; i > 99; i -= 11)                             {                                 if (n % i == 0)                                 {                                     int t = n / i;                                     if (t < 1000) return n;                                 }                             }                         }                     }                 }             }             return 0;         } }