import std.stdio;
import std.math;

class tarray
{
	private size_t arr_size;
	private size_t arr0_size;
	private size_t arr1_size;
	private size_t arr2_size;

	private size_t[] arr;

	this(size_t size)
	{
		arr_size = size;
		arr0_size = size - 1;
		arr1_size = size - 2;
		arr2_size = size / 2;
		arr.length = (size * size) / 2;
	}

	bool safe(size_t x, size_t y)
	{
		if (x != y && x > y)
			if (x < arr_size)
				if (y < arr_size)
					return true;
		return false;
	}

	size_t get_index(size_t x, size_t y)
	{
		if (y >= arr2_size)
			return (arr_size * (arr1_size - y)) + (arr0_size - x);
		return (arr_size * y) + x;
	}

	bool get_index_xy(size_t index, ref size_t x, ref size_t y)
	{
		if (index >= arr.length)
			return false;

		y = index / arr_size;
		x = index % arr_size;
		if(x < y || x == y)
		{
			x = arr0_size - x;
			y = arr1_size - y;
		}
		return true;
	}

	auto insert(size_t x, size_t y, size_t value)
	{
		if (!safe(x, y))
			return size_t.max;

		auto index = get_index(x, y);
		debug writeln("index for(", x, ", ", y, ") = ", index);
		arr[index] = value;
		return index;
	}

	auto get(size_t x, size_t y)
	{
		if (!safe(x, y))
			return size_t.max;

		return arr[get_index(x, y)];
	}

	auto get(size_t index)
	{
		if (index >= arr.length)
			return size_t.max;

		return arr[index];
	}

	void print()
	{
		for (size_t y = 0; y < arr2_size; ++y)
		{
			auto start = arr_size * y;
			auto end = arr_size * (y + 1);
			writeln(arr[start .. end]);
		}
	}
}

void main()
{
	size_t size = 7;
	tarray ta = new tarray(size);

	auto sx = 0;
	auto k = 1;
	for (size_t y = 0; y < size; ++y)
	{
		for (size_t x = sx; x < size; ++x)
		{
			if (ta.insert(x, y, k))
				k++;
		}
		sx++;
	}

	ta.print();

	//test 1
	size_t tx = 2;
	size_t ty = 0;
	size_t rx, ry;
	auto index = ta.get_index(tx, ty);
	ta.get_index_xy(index, rx, ry);
	if(rx != tx || ry != ty)
	{
		writeln("WTF!? (index=",index,") x=",rx," y=", ry);
	}

	//test 2
	tx = 4;
	ty = 3;
	index = ta.get_index(tx, ty);
	ta.get_index_xy(index, rx, ry);
	if(rx != tx || ry != ty)
	{
		writeln("WTF!? (index=",index,") x=",rx," y=", ry);
	}
}