Solution to problem 2 part 1 in Python

src/Year_2016/P2.py

@@ -0,0 +1,121 @@
+# --- Day 2: Bathroom Security ---
+
+# You arrive at Easter Bunny Headquarters under cover of darkness. However, you
+# left in such a rush that you forgot to use the bathroom! Fancy office
+# buildings like this one usually have keypad locks on their bathrooms, so you
+# search the front desk for the code.
+
+# "In order to improve security," the document you find says, "bathroom codes
+# will no longer be written down. Instead, please memorize and follow the
+# procedure below to access the bathrooms."
+
+# The document goes on to explain that each button to be pressed can be found
+# by starting on the previous button and moving to adjacent buttons on the
+# keypad: U moves up, D moves down, L moves left, and R moves right. Each line
+# of instructions corresponds to one button, starting at the previous button
+# (or, for the first line, the "5" button); press whatever button you're on at
+# the end of each line. If a move doesn't lead to a button, ignore it.
+
+# You can't hold it much longer, so you decide to figure out the code as you
+# walk to the bathroom. You picture a keypad like this:
+
+# 1 2 3
+# 4 5 6
+# 7 8 9
+
+# Suppose your instructions are:
+
+# ULL
+# RRDDD
+# LURDL
+# UUUUD
+
+#     You start at "5" and move up (to "2"), left (to "1"), and left (you
+# can't, and stay on "1"), so the first button is 1.
+#     Starting from the previous button ("1"), you move right twice (to "3")
+# and then down three times (stopping at "9" after two moves and ignoring the
+# third), ending up with 9.
+#     Continuing from "9", you move left, up, right, down, and left, ending
+# with 8.
+#     Finally, you move up four times (stopping at "2"), then down once, ending
+# with 5.
+
+# So, in this example, the bathroom code is 1985.
+
+# Your puzzle input is the instructions from the document you found at the
+# front desk. What is the bathroom code?
+
+from typing import Optional, Tuple
+
+with open("files/P2.txt") as f:
+    instructions = [line for line in f.read().strip().split()]
+
+
+def move_right(position: Tuple[int, int]) -> Tuple[int, int]:
+    _x = position[0] + 1
+    if 0 <= _x <= 2:
+        return _x, position[1]
+    else:
+        return position[0], position[1]
+
+
+def move_down(position: Tuple[int, int]) -> Tuple[int, int]:
+    _y = position[1] - 1
+    if 0 <= _y <= 2:
+        return position[0], _y
+    else:
+        return position[0], position[1]
+
+
+def move_left(position: Tuple[int, int]) -> Tuple[int, int]:
+    _x = position[0] - 1
+    if 0 <= _x <= 2:
+        return _x, position[1]
+    else:
+        return position[0], position[1]
+
+
+def move_up(position: Tuple[int, int]) -> Tuple[int, int]:
+    _y = position[1] + 1
+    if 0 <= _y <= 2:
+        return position[0], _y
+    else:
+        return position[0], position[1]
+
+
+def pos2num(position: Tuple[int, int]) -> Optional[int]:
+    num_dict = {
+        1: (0, 2),
+        2: (1, 2),
+        3: (2, 2),
+        4: (0, 1),
+        5: (1, 1),
+        6: (1, 2),
+        7: (0, 0),
+        8: (1, 0),
+        9: (2, 0),
+    }
+    return next((k for k, v in num_dict.items() if v == position), None)
+
+
+def part_1() -> None:
+    secret = []
+    for instruction in instructions:
+        # 0,0 is the x,y coordinates of the bottom left position
+        pos = (1, 1)
+        for button in instruction:
+            if button == "D":
+                pos = move_down(pos)
+            elif button == "U":
+                pos = move_up(pos)
+            elif button == "R":
+                pos = move_right(pos)
+            elif button == "L":
+                pos = move_left(pos)
+        secret.append(pos)
+    secret_code = "".join(map(str, (pos2num(num) for num in secret)))
+    print(f"The secret code is {secret_code}")
+
+
+if __name__ == "__main__":
+    part_1()