Add solution for 2nd day

02/example

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+A Y
+B X
+C Z
+

02/rps.py

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+
+from enum import IntEnum
+import fileinput
+from typing import Iterable
+
+SCORE_WIN = 6
+SCORE_DRAW = 3
+SCORE_LOSS = 0
+
+class Choice(IntEnum):
+    ROCK = 1
+    PAPER = 2
+    SCISSOR = 3
+
+def letter_to_choice(letter: str) -> Choice:
+    letter = ord(letter)
+    if letter > 67:
+        letter += 1
+    return Choice(letter & 3)
+
+def get_better(i: Choice) -> Choice:
+    return i + 1 if i != 3 else 1
+
+def rps(opponent: Choice, me: Choice) -> int:
+    """Return score for given RPS match"""
+    if opponent == me: # Draw
+        return SCORE_DRAW + me.value
+    elif get_better(opponent) == me:
+        return SCORE_WIN + me.value
+    else:
+        return SCORE_LOSS + me.value
+
+def get_correct(opponent: Choice, goal: str) -> Choice:
+    if goal == "Y": # draw
+        return Choice(opponent)
+    elif goal == "Z": # win
+        return Choice(get_better(opponent))
+    else: # lose
+        return Choice(get_better(get_better(opponent)))
+
+def solve(lines: Iterable[str]) -> int:
+    total_score = 0
+    for line in lines:
+        if len(line) == 4:
+            total_score += rps(letter_to_choice(line[0]), letter_to_choice(line[2]))
+    return total_score
+    
+def solveb(lines: Iterable[str]) -> int:
+    total_score = 0
+    for line in lines:
+        if len(line) == 4:
+            total_score += rps(letter_to_choice(line[0]), get_correct(letter_to_choice(line[0]), line[2]))
+    return total_score
+
+if __name__ == "__main__":
+    print(solve(fileinput.input()))
+    print(solveb(fileinput.input()))