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http://projecteuler.net/problem=12
What is the value of the first triangle number to have over five hundred divisors?
int max = 0; int n = 1; while(true) { double value = (.5 * n) * (n + 1); int devisor_count = 0; for (int i = 1; i <= value; i++) { if (value % i == 0) devisor_count++; } if (max < devisor_count) { max = devisor_count; Console.WriteLine(n + " value " + value + " devisor Count :" + devisor_count); } if (devisor_count > 500) { Console.WriteLine(n + " value " + value + " FINAL devisor Count :" + devisor_count); break; } n++; } |
http://projecteuler.net/problem=41
We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital and is also prime.
What is the largest n-digit pandigital prime that exists?
static void Main(string[] args) { int n = 1; while (true) { if (isPrime(n)) { if (Order(n)) Console.WriteLine(n); } n++; } } public static bool Order(int n) { string mynum = ""+n; int [] int_array = new int[mynum.Length]; for (int i = 0; i < mynum.Length; i++) int_array[i] = int.Parse(mynum[i].ToString()); Array.Sort(int_array); if (int_array[0] == 1) { int count = 2; for (int j = 1; j < int_array.Length; j++) { if (count == int_array[j]) count++; else return false; } } else return false; return true; } public static bool isPrime(int n) { if (n == 1) return false; if (n == 2) return true; for (int i = 2; i < n; ++i) { if ((n % i) == 0) return false; } return true; } |