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Euler12.cs
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Euler12.cs
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using System;
using System.Collections.Generic;
using System.Linq;
namespace euler
{
class Euler12
{
public static void Main ()
{
foreach (int i in trianglenumbers()) {
var n = gettreenumber (i);
var divs = n.allDivisors;
Console.Write (n.i.ToString ().PadLeft (7) + " ("+divs.Count().ToString().PadLeft(3)+"): ");
foreach (treenumber div in divs) {
Console.Write (div.i + ",");
}
Console.Write ("\n");
if (divs.Count() > 500) {
Console.WriteLine(">500!");
break;
}
}
}
static IEnumerable<int> trianglenumbers ()
{
int last = 0;
for (int i = 1; i <= int.MaxValue; i++) {
yield return last += i;
}
}
static HashSet<treenumber> treenumbers = new HashSet<treenumber> ();
static treenumber gettreenumber (int i)
{
foreach (treenumber treenumber in treenumbers)
if (treenumber.i == i)
return treenumber;
var newtreenumber = new treenumber (i);
treenumbers.Add (newtreenumber);
return newtreenumber;
}
class treenumber
{
public treenumber (int i)
{
this.i = i;
if (i == 1) {
_directDivisors = new HashSet<treenumber> (){};
_allDivisors = new HashSet<treenumber> (){this};
} else if (i == 2) {
_directDivisors = new HashSet<treenumber> (){gettreenumber (1)};
_allDivisors = new HashSet<treenumber> (){gettreenumber (1)};
} else {
_directDivisors = null;
_allDivisors = null;
}
}
public int i;
HashSet<treenumber> _directDivisors;
public HashSet<treenumber> directDivisors {
get {
//Console.WriteLine ("Checking " + i + ".directDivisors");
if (_directDivisors != null)
return _directDivisors;
_directDivisors = new HashSet<treenumber> ();
var possibledivs = Enumerable.Range (1, (i + 1) / 2).ToList ();
while (possibledivs.Count() > 0) {
int n = possibledivs [possibledivs.Count () - 1];
if (i % n == 0) {
var newtreenumber = gettreenumber (n);
_directDivisors.Add (newtreenumber);
foreach (treenumber div in newtreenumber.allDivisors) {
possibledivs.Remove (div.i);
}
}
possibledivs.Remove (n);
}
return _directDivisors;
}
}
HashSet<treenumber> _allDivisors;
public HashSet<treenumber> allDivisors {
get {
//Console.WriteLine ("Checking " + i + ".allDivisors");
if (_allDivisors != null)
return _allDivisors;
_allDivisors = new HashSet<treenumber> ();
foreach (treenumber div in directDivisors) {
_allDivisors.Add (div);
_allDivisors.UnionWith (div.allDivisors);
}
_allDivisors.Add (this);
return _allDivisors;
}
}
public override string ToString ()
{
return i.ToString ();
}
}
}
}