From 58ee9f48c4c90352bccdb1cc88d7b9ef923f9216 Mon Sep 17 00:00:00 2001
From: bd <bdunahu@operationnull.com>
Date: Mon, 10 Jun 2024 12:26:20 -0600
Subject: AoC 2015.3 p1+2

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+See: https://adventofcode.com/2015/day/3
+** Part 1
+*** Purpose
+Given a list of directional arrows:
+
+#+begin_example
+^>><v
+#+end_example
+
+Determine how many unique spaces on a grid are reached.
+
+*** Method
+
+As a more creative solution, we can use closure to create an environment which keeps track of visited spaces. Say this environment contains an initial variable with this value:
+
+#+begin_example
+'((0 . 0))
+#+end_example
+
+And we translate each instruction to a different pair of values, each representing a direction.
+
+^>><v:
+
+#+begin_example
+'((0 . 1)
+  (1 . 0)
+  (1 . 0)
+  (-1 . 0)
+  (0 . -1))
+#+end_example
+
+Then simply call the procedure that is encapsulated by a local environment, and have it add the cons pair to the previous and update its internal state.
+
+Finally, we can have another procedure that returns the length of the local list.
+
+** Part 2
+*** Purpose
+The next part claims we now have two visitors. Each of them take turns receiving directions. I chose an object-like approach for part one because the original problem claimed we were tracking "Santa" visiting houses---this is a good thing, which truly shines now that we have two visitors.
+
+*** Method
+All we need to do is change the main function to create multiple visitors, store them in a list, and cycle through the list of visitors when we process instructions.
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