public override object Solution()
{
// a quick look-up table of which perimeters (values of P) have been found and how frequently
Dictionary<int, int> counter = new Dictionary<int, int>();
// we'll go ahead and check A and B to 500 even though that would never work (e.g. 500^2 + 500^2 = C^2 ??)
foreach (int a in Enumerable.Range(1, 500))
{
foreach (int b in Enumerable.Range(1, 500))
{
var t = new Triangle()
{
A = a,
B = b
};
// if this is a valid right triangle and the perimeter is less than 1000 as described
if (t.Check && t.P <= 1000)
{
if (!counter.ContainsKey(t.P))
{
counter.Add(t.P, 0);
}
counter[t.P] += 1;
}
}
}
return counter.OrderByDescending(t => t.Value).First().Key;
}
int GetTriangleMaxSum(Triangle t)
{
if (t == null)
return 0;
if (maxSums.ContainsKey(t))
return maxSums[t];
if (t.leftClosed || t.left == null)
return t.value + GetTriangleMaxSum(t.right);
if (t.rightClosed || t.right == null)
return t.value + GetTriangleMaxSum(t.left);
if (t.left.value > t.right.value)
t.right.leftClosed = true;
else
t.left.rightClosed = true;
int leftSum = GetTriangleMaxSum(t.left);
int rightSum = GetTriangleMaxSum(t.right);
int s = t.value + (leftSum > rightSum ? leftSum : rightSum);
maxSums.Add(t, s);
return s;
}
public Triangle(List<int[]> lines)
{
List<Triangle> lastTriangleLine = new List<Triangle>();
for (int i = lines.Count - 1; i > 0; i--)
{
List<Triangle> nextTriangleLine = new List<Triangle>();
for (int j = 0; j <= i; j++)
{
Triangle t = new Triangle(lines[i][j]);
if (i < lines.Count - 1)
{
t.left = lastTriangleLine[j];
t.right = lastTriangleLine[j + 1];
}
nextTriangleLine.Add(t);
}
lastTriangleLine = new List<Triangle>(nextTriangleLine);
}
value = lines[0][0];
left = lastTriangleLine[0];
right = lastTriangleLine[1];
}
public Triangle(int value, Triangle left, Triangle right)
{
this.value = value;
this.left = left;
this.right = right;
}
public static Triangle Read(List<int[]> lines, int currentLine, int currentPos, int size)
{
Triangle t = new Triangle(lines[currentLine][currentPos]);
if (size == 1)
return t;
t.left = Triangle.Read(lines, currentLine + 1, currentPos, size - 1);
t.right = Triangle.Read(lines, currentLine + 1, currentPos + 1, size - 1);
return t;
}