day 3

solutions/2/README.md

@@ -5,13 +5,6 @@ Just some simple parsing.
 
 The second one is similar, but we can be more efficient if we XOR the first and second position.
 
-# 2
-
-For the first we can simply count the occurrences and see if they are between the accepted values.
-Just some simple parsing.
-
-The second one is similar, but we can be more efficient if we XOR the first and second position.
-
 <details>
   <summary>Solutions</summary>
   <ol>

solutions/3/README.md

@@ -0,0 +1,16 @@
+# 3
+
+We can simply parse the forest as an array of strings.
+The trees repeat infinitely to the right, this screams for a good mod.
+This means: `char = row[x % len(row)]`. No complex logic needed
+
+For the second one we simply automate the process and sum up the total.
+We can simply encode the coordinates as a function of the index we are current at.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>252</li>
+    <li>57 * 252 * 64 * 66 * 43 = 2608962048</li>
+  </ol>
+</details>

solutions/3/main.py

@@ -0,0 +1,50 @@
+from typing import Dict, List
+from os.path import join, dirname
+from functools import reduce
+
+
+class Forest():
+
+    def __init__(self, text: str) -> None:
+        self.text = text.strip().split('\n')
+
+    @property
+    def height(self) -> int:
+        return len(self.text)
+
+    def is_tree_at(self, y: int, x: int) -> bool:
+        if y > self.height:
+            return False
+        row = self.text[y]
+        return row[x % len(row)] == '#'
+
+
+data = join(dirname(__file__), 'data.txt')
+with open(data) as f:
+    forest = Forest(f.read())
+
+    # 1
+    trees: int = 0
+    for y in range(forest.height):
+        is_tree: bool = forest.is_tree_at(y, y*3)
+        if is_tree:
+            trees += 1
+    print(f'Result Simple: {trees}')
+
+    # 2
+    all: Dict[str, int] = {
+        '11': 0,
+        '13': 0,
+        '15': 0,
+        '17': 0,
+        '21': 0,
+    }
+    for i in range(forest.height):
+        for key, value in all.items():
+            dy, dx = map(int, list(key))
+            y = i * dy
+            x = i * dx
+            if forest.is_tree_at(y, x):
+                all[key] += 1
+    total = reduce((lambda x, y: x * y), all.values())
+    print(f'Result Combined: {list(all.values())} = {total}')