AoC 2024 Day 15

# output is sum of each box's y index * 100 + x index

# part 1
grid = []
moves = []
with open("day15input.txt") as f:
    input_lines = f.read().splitlines()
    first_part = True
    for line in input_lines:
        if not line:
            first_part = False
            continue
        if first_part:
            grid.append(list(line))
        else:
            moves.append(line)
    moves = "".join(moves)

def sum_gps_coordinates(matrix: list[list[str]], instructions: str) -> int:
    step = {'<': (0, -1), 'v': (1, 0), '>': (0, 1), '^': (-1, 0)}

    rows = len(matrix)
    cols = len(matrix[0])

    curr_pos = (-1, -1)
    for y in range(rows):
        for x in range(cols):
            if matrix[y][x] == '@':
                curr_pos = (y, x)
                break
        if curr_pos != (-1, -1):
            break

    for i in instructions:
        y1, x1 = curr_pos
        dy, dx = step[i]
        y2, x2 = y1 + dy, x1 + dx  # this is the adjacent tile in the same direction

        if matrix[y2][x2] == "O":
            y3, x3 = y2 + dy, x2 + dx  # this is the next tile in the same direction
            while matrix[y3][x3] != '#':
                if matrix[y3][x3] == '.':
                    matrix[y2][x2], matrix[y3][x3] = matrix[y3][x3], matrix[y2][x2]
                    break
                y3, x3 = y3 + dy, x3 + dx
        if matrix[y2][x2] == '.':
            matrix[y1][x1], matrix[y2][x2] = matrix[y2][x2], matrix[y1][x1]
            curr_pos = y2, x2

    # after all moves, calculate output
    output = 0
    for y in range(rows):
        for x in range(cols):
            if matrix[y][x] == 'O':
                output += y * 100 + x

    return output


print(sum_gps_coordinates(grid, moves))



# part 2
wide_grid = []
moves = []
with open("day15input.txt") as f:
    input_lines = f.read().splitlines()
    first_part = True
    for line in input_lines:
        if not line:
            first_part = False
        elif not first_part:
            moves.append(line)
        elif first_part:
            temp = []
            for char in line:
                if char == "O":
                    temp.extend(["[", "]"])
                elif char == "#":
                    temp.extend(["#"] * 2)
                elif char == ".":
                    temp.extend(["."] * 2)
                elif char == "@":
                    temp.extend(["@", "."])
            wide_grid.append(temp)
    moves = "".join(moves)


def sum_gps_coordinates2(matrix: list[list[str]], instructions: str) -> int:
    def push(stack: list[list[tuple[int, int]]], direction: str):
        nonlocal matrix, step
        offset = step[direction]
        if direction == "<" or direction == ">":
            stack = stack[0]
            y3, x3 = stack[-1]
            while matrix[y3][x3] != '#' and matrix[y3][x3] != '.':
                x3 += offset[1]
                stack.append((y3, x3))
            if matrix[y3][x3] == '#':
                return
            else:
                curr_y, curr_x = y3, x3
                while stack:
                    next_y, next_x = stack.pop()
                    matrix[curr_y][curr_x], matrix[next_y][next_x] = matrix[next_y][next_x], matrix[curr_y][curr_x]
                    curr_y, curr_x = next_y, next_x
                return
        elif direction == '^' or direction == 'v':
            temp = {(1, 1)}
            while temp:
                temp = set()
                for coord in stack[-1]:
                    if matrix[coord[0] + offset[0]][coord[1]] == '#':
                        return
                    if matrix[coord[0] + offset[0]][coord[1]] == '[':
                        temp.add((coord[0] + offset[0], coord[1]))
                        temp.add((coord[0] + offset[0], coord[1] + 1))
                    elif matrix[coord[0] + offset[0]][coord[1]] == ']':
                        temp.add((coord[0] + offset[0], coord[1]))
                        temp.add((coord[0] + offset[0], coord[1] - 1))
                stack.append(list(temp))
            stack.pop()
            while stack:
                curr_tiles = stack.pop()
                for tile in curr_tiles:
                    (matrix[tile[0]][tile[1]],
                     matrix[tile[0]+offset[0]][tile[1]]) = (matrix[tile[0]+offset[0]][tile[1]],
                                                            matrix[tile[0]][tile[1]])
        return

    step = {'<': (0, -1), 'v': (1, 0), '>': (0, 1), '^': (-1, 0)}

    rows = len(matrix)
    cols = len(matrix[0])

    # find starting position
    curr_pos = (-1, -1)
    for y in range(rows):
        for x in range(cols):
            if matrix[y][x] == '@':
                curr_pos = (y, x)
                break
        if curr_pos != (-1, -1):
            break

    # execute instructions
    for i in instructions:
        y1, x1 = curr_pos
        dy, dx = step[i]
        y2, x2 = y1 + dy, x1 + dx  # this is the adjacent tile in the current direction
        if matrix[y2][x2] == "[":
            push([[(y2, x2), (y2, x2+1)]], i)
        elif matrix[y2][x2] == "]":
            temp = []
            temp.append([(y2, x2), (y2, x2-1)])
            push([[(y2, x2), (y2, x2-1)]], i)
        if matrix[y2][x2] == '.':
            matrix[y1][x1], matrix[y2][x2] = matrix[y2][x2], matrix[y1][x1]
            curr_pos = y2, x2

    # after all moves, calculate output
    output = 0
    for y in range(rows):
        for x in range(cols):
            if matrix[y][x] == '[':
                output += y * 100 + x

    return output


print(sum_gps_coordinates2(wide_grid, moves))