Add solution for day 2

day2/part1.py

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+"""
+--- Day 2: Rock Paper Scissors ---
+
+The Elves begin to set up camp on the beach. To decide whose tent gets
+to be closest to the snack storage, a giant Rock Paper Scissors
+tournament is already in progress.
+
+Rock Paper Scissors is a game between two players. Each game contains
+many rounds; in each round, the players each simultaneously choose one
+of Rock, Paper, or Scissors using a hand shape. Then, a winner for that
+round is selected: Rock defeats Scissors, Scissors defeats Paper, and
+Paper defeats Rock. If both players choose the same shape, the round
+instead ends in a draw.
+
+Appreciative of your help yesterday, one Elf gives you an encrypted
+strategy guide (your puzzle input) that they say will be sure to help
+you win. "The first column is what your opponent is going to play: A
+for Rock, B for Paper, and C for Scissors. The second column--"
+Suddenly, the Elf is called away to help with someone's tent.
+
+The second column, you reason, must be what you should play in
+response: X for Rock, Y for Paper, and Z for Scissors. Winning every
+time would be suspicious, so the responses must have been carefully
+chosen.
+
+The winner of the whole tournament is the player with the highest
+score. Your total score is the sum of your scores for each round. The
+score for a single round is the score for the shape you selected (1 for
+Rock, 2 for Paper, and 3 for Scissors) plus the score for the outcome
+of the round (0 if you lost, 3 if the round was a draw, and 6 if you
+won).
+
+Since you can't be sure if the Elf is trying to help you or trick you,
+you should calculate the score you would get if you were to follow the
+strategy guide.
+
+For example, suppose you were given the following strategy guide:
+
+A Y
+B X
+C Z
+
+This strategy guide predicts and recommends the following:
+
+- In the first round, your opponent will choose Rock (A), and you
+  should choose Paper (Y). This ends in a win for you with a score of 8
+  (2 because you chose Paper + 6 because you won).
+- In the second round, your opponent will choose Paper (B), and you
+  should choose Rock (X). This ends in a loss for you with a score of 1
+  (1 + 0).
+- The third round is a draw with both players choosing Scissors, giving
+  you a score of 3 + 3 = 6.
+
+In this example, if you were to follow the strategy guide, you would
+get a total score of 15 (8 + 1 + 6).
+
+What would your total score be if everything goes exactly according to
+your strategy guide?
+"""
+
+OPPONENT_ROCK = "A"
+OPPONENT_PAPER = "B"
+OPPONENT_SCISSORS = "C"
+
+LOSS = 0
+DRAW = 1
+WIN = 2
+
+YOU_ROCK = "X"
+YOU_PAPER = "Y"
+YOU_SCISSORS = "Z"
+
+POINTS = {
+    YOU_ROCK: 1,
+    YOU_PAPER: 2,
+    YOU_SCISSORS: 3
+}
+
+LOSS_POINTS = 0
+DRAW_POINTS = 3
+WIN_POINTS = 6
+
+RESULTS = {
+    f"{OPPONENT_ROCK}{YOU_ROCK}": DRAW,
+    f"{OPPONENT_ROCK}{YOU_PAPER}": WIN,
+    f"{OPPONENT_ROCK}{YOU_SCISSORS}": LOSS,
+    f"{OPPONENT_PAPER}{YOU_ROCK}": LOSS,
+    f"{OPPONENT_PAPER}{YOU_PAPER}": DRAW,
+    f"{OPPONENT_PAPER}{YOU_SCISSORS}": WIN,
+    f"{OPPONENT_SCISSORS}{YOU_ROCK}": WIN,
+    f"{OPPONENT_SCISSORS}{YOU_PAPER}": LOSS,
+    f"{OPPONENT_SCISSORS}{YOU_SCISSORS}": DRAW,
+}
+
+REQUIRED_ACTIONS = {
+    "X": LOSS,
+    "Y": DRAW,
+    "Z": WIN,
+}
+
+DESIRED_RESULTS = {
+    f"{OPPONENT_ROCK}X": YOU_SCISSORS,
+    f"{OPPONENT_ROCK}Y": YOU_ROCK,
+    f"{OPPONENT_ROCK}Z": YOU_PAPER,
+    f"{OPPONENT_PAPER}X": YOU_ROCK,
+    f"{OPPONENT_PAPER}Y": YOU_PAPER,
+    f"{OPPONENT_PAPER}Z": YOU_SCISSORS,
+    f"{OPPONENT_SCISSORS}X": YOU_PAPER,
+    f"{OPPONENT_SCISSORS}Y": YOU_SCISSORS,
+    f"{OPPONENT_SCISSORS}Z": YOU_ROCK,
+}
+
+
+def main():
+    points = 0
+
+    with open("input.txt", "r", encoding="utf-8") as f:
+        for line in f:
+            if not line.strip():
+                continue
+
+            opponent, you = line.strip().split()
+            points += POINTS[you]
+            action_code = f"{opponent}{you}"
+            if RESULTS[action_code] == LOSS:
+                points += LOSS_POINTS
+            elif RESULTS[action_code] == DRAW:
+                points += DRAW_POINTS
+            elif RESULTS[action_code] == WIN:
+                points += WIN_POINTS
+
+    print(f"You got {points} points")
+
+
+if __name__ == "__main__":
+    main()

day2/part2.py

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+"""
+--- Part Two ---
+
+The Elf finishes helping with the tent and sneaks back over to you.
+"Anyway, the second column says how the round needs to end: X means you
+need to lose, Y means you need to end the round in a draw, and Z means
+you need to win. Good luck!"
+
+The total score is still calculated in the same way, but now you need to
+figure out what shape to choose so the round ends as indicated. The
+example above now goes like this:
+
+- In the first round, your opponent will choose Rock (A), and you need
+  the round to end in a draw (Y), so you also choose Rock. This gives
+  you a score of 1 + 3 = 4.
+- In the second round, your opponent will choose Paper (B), and you
+  choose Rock so you lose (X) with a score of 1 + 0 = 1.
+- In the third round, you will defeat your opponent's Scissors with
+  Rock for a score of 1 + 6 = 7.
+
+Now that you're correctly decrypting the ultra top secret strategy
+guide, you would get a total score of 12.
+
+Following the Elf's instructions for the second column, what would your
+total score be if everything goes exactly according to your strategy
+guide?
+"""
+
+OPPONENT_ROCK = "A"
+OPPONENT_PAPER = "B"
+OPPONENT_SCISSORS = "C"
+
+LOSS = 0
+DRAW = 1
+WIN = 2
+
+YOU_ROCK = "X"
+YOU_PAPER = "Y"
+YOU_SCISSORS = "Z"
+
+POINTS = {
+    YOU_ROCK: 1,
+    YOU_PAPER: 2,
+    YOU_SCISSORS: 3
+}
+
+LOSS_POINTS = 0
+DRAW_POINTS = 3
+WIN_POINTS = 6
+
+RESULTS = {
+    f"{OPPONENT_ROCK}{YOU_ROCK}": DRAW,
+    f"{OPPONENT_ROCK}{YOU_PAPER}": WIN,
+    f"{OPPONENT_ROCK}{YOU_SCISSORS}": LOSS,
+    f"{OPPONENT_PAPER}{YOU_ROCK}": LOSS,
+    f"{OPPONENT_PAPER}{YOU_PAPER}": DRAW,
+    f"{OPPONENT_PAPER}{YOU_SCISSORS}": WIN,
+    f"{OPPONENT_SCISSORS}{YOU_ROCK}": WIN,
+    f"{OPPONENT_SCISSORS}{YOU_PAPER}": LOSS,
+    f"{OPPONENT_SCISSORS}{YOU_SCISSORS}": DRAW,
+}
+
+REQUIRED_ACTIONS = {
+    "X": LOSS,
+    "Y": DRAW,
+    "Z": WIN,
+}
+
+DESIRED_RESULTS = {
+    f"{OPPONENT_ROCK}X": YOU_SCISSORS,
+    f"{OPPONENT_ROCK}Y": YOU_ROCK,
+    f"{OPPONENT_ROCK}Z": YOU_PAPER,
+    f"{OPPONENT_PAPER}X": YOU_ROCK,
+    f"{OPPONENT_PAPER}Y": YOU_PAPER,
+    f"{OPPONENT_PAPER}Z": YOU_SCISSORS,
+    f"{OPPONENT_SCISSORS}X": YOU_PAPER,
+    f"{OPPONENT_SCISSORS}Y": YOU_SCISSORS,
+    f"{OPPONENT_SCISSORS}Z": YOU_ROCK,
+}
+
+
+def main():
+    points = 0
+
+    with open("input.txt", "r", encoding="utf-8") as f:
+        for line in f:
+            if not line.strip():
+                continue
+
+            opponent, desired_result = line.strip().split()
+            result = REQUIRED_ACTIONS[desired_result]
+            if result == DRAW:
+                points += DRAW_POINTS
+            elif result == WIN:
+                points += WIN_POINTS
+
+            my_action = DESIRED_RESULTS[f"{opponent}{desired_result}"]
+            points += POINTS[my_action]
+
+    print(f"Using the complete strategy guide, my score will be {points}")
+
+
+if __name__ == "__main__":
+    main()

day2/testinput.txt

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+A Y
+B X
+C Z