Avent of Code - Day 09 - Rope Bridge

Advent of Code occurs at Dec 01 to 25 where each day, you will need to solve a puzzle. It is Festival and the problem statement is mostly related to Christmas.

Day 09 - Rope Bridge

https://adventofcode.com/2022/day/9

Q1

import sys

file1 = open(sys.argv[1], "r")

seen = set()

H = (0, 0)
T = (0, 0)
seen.add(tuple(T))
prevH = H

while True:
        line = file1.readline()
        if not line:
                break
        a, b = line.strip().split()
        for _ in range(int(b)):
                prevH = H
                if a == "R":
                        H = (H[0], H[1] + 1)
                elif a == "U":
                        H = (H[0] - 1, H[1])
                elif a == "L":
                        H = (H[0], H[1] - 1)
                elif a == "D":
                        H = (H[0] + 1, H[1])

                if abs(H[0] - T[0]) <= 1 and abs(H[1] - T[1]) <= 1:
                        continue
                T = prevH
                seen.add(tuple(T))

print(len(seen))

Q2

import sys
from collections import deque
from math import inf

file1 = open(sys.argv[1], "r")
seen = set()

snake = [(0, 0) for _ in range(10)]
seen.add(snake[0])

def get_near(A, B):
        rr, cc = A
        r, c = B
        def dis(r0, c0, r1, c1):
                return abs(r0 - r1) + abs(c0 - c1)
        D = inf
        for dr in range(-1, 2):
                for dc in range(-1, 2):
                        if dr != 0 or dc != 0:
                                d = dis(rr + dr, cc + dc, r, c)
                                if d < D:
                                        D = d
                                        ans = (rr + dr, cc + dc)
        return ans


while True:
        line = file1.readline()
        if not line:
                break
        a, b = line.strip().split()
        for _ in range(int(b)):
                x = snake[-1]
                if a == "R":
                        H = (x[0], x[1] + 1)
                elif a == "U":
                        H = (x[0] - 1, x[1])
                elif a == "L":
                        H = (x[0], x[1] - 1)
                elif a == "D":
                        H = (x[0] + 1, x[1])
                snake[-1] = H
                for i in range(8, -1, -1):
                        if (abs(snake[i][0] - snake[i + 1][0]) <= 1) and abs(snake[i][1] - snake[i + 1][1]) <= 1:
                                break
                        snake[i] = get_near(snake[i], snake[i + 1])
                seen.add(snake[0])

print(len(seen))

Q1 is basically a snake game. However, the Q2 is tricky - the body movement needs to be based on the rules, and not just follow its previous piece.

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Steem to the Moon!