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- XAML code snippets

Project Euler problem 21~

`1: class Program`

2: {3: static void Main(string[] args)4: {`5: var sw = new Stopwatch();`

6:`7: Console.WriteLine("The sum of all the amicable numbers under 10000");`

8: sw.Start();9: var sum1 = test(10000);10: sw.Stop();11: Console.WriteLine(string.Format("construct all divisor map and then match way(tick:{0}): {1}", sw.ElapsedTicks, sum1));12:13: sw.Reset();14:`15: Console.WriteLine("Press any key to exit");`

16: Console.ReadKey();17: }18:`19: /// <summary>`

`20: /// basically find out all the divisor for each number from 1 to 10000 by using`

`21: /// sieve of eratosthenes way of constructing a dictionary of number as key and value is list of divisors`

`22: /// next step is iterate the dictionary and find out all the amicable pairs and store them in a list`

`23: /// sum of list is the answer!`

`24: /// </summary>`

`25: /// <param name="ceiling"></param>`

`26: /// <returns></returns>`

27: static int test(int ceiling)28: {29: var map = new List<int>[ceiling + 1];30: var div = 0;31: int bound = (int)Math.Sqrt(ceiling);32: for (int i = 1; i <= bound; i++)33: {34: for (int j = i * i; j <= ceiling; j += i)35: {36: if (map[j] == null)37: map[j] = new List<int>();38:39: map[j].Add(i);40: div = j / i;41: if (div < j && map[j].Any(l => l == div) == false)42: map[j].Add(div);43: }44: }45: var sum = 0;46: var pairs = new List<int>();47: for (int i = 2; i < ceiling; i++)48: {49: sum = map[i].Sum();`50: if (sum < ceiling && sum != i && map[sum].Sum() == i)`

51: {52: if (pairs.Contains(sum) == false)53: pairs.Add(sum);54: if (pairs.Contains(i) == false)55: pairs.Add(i);56: }57: }`58: return pairs.Sum();`

59: }60: }