day23 better way to check moveable elves
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Ruediger Ludwig
parent
840e7abc4d
commit
867a476c44
2 changed files with 97 additions and 75 deletions
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@ -76,6 +76,16 @@ class Position:
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yield self.left()
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yield self.down()
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def all_neighbors(self) -> Iterator[Position]:
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yield Position(self.x + 1, self.y)
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yield Position(self.x + 1, self.y - 1)
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yield Position(self.x, self.y - 1)
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yield Position(self.x - 1, self.y - 1)
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yield Position(self.x - 1, self.y)
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yield Position(self.x - 1, self.y + 1)
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yield Position(self.x, self.y + 1)
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yield Position(self.x + 1, self.y + 1)
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def is_within(self, top_left: Position, bottom_right: Position) -> bool:
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"""
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Checks if this point is within the rectangle spanned by the given positions.
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@ -3,7 +3,7 @@ from dataclasses import dataclass
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from enum import IntEnum
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from itertools import count, cycle
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from typing import Iterable, Iterator
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from typing import Iterator
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from advent.common.position import Position
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@ -58,52 +58,33 @@ class Ground:
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return result[:-1]
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@classmethod
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def check_adjacent(cls, elves: Iterable[Position],
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position: Position) -> list[Direction] | None:
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north = False
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south = False
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west = False
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east = False
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if (position + Position(-1, -1)) in elves:
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north = True
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west = True
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if (position + Position(1, 1)) in elves:
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south = True
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east = True
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if north is False:
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north = (position + Position(0, -1)) in elves
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if south is False:
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south = (position + Position(0, 1)) in elves
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if west is False:
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west = (position + Position(-1, 0)) in elves
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if east is False:
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east = (position + Position(1, 0)) in elves
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if north is False or east is False:
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if (position + Position(1, -1)) in elves:
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north = True
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east = True
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if south is False or west is False:
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if (position + Position(-1, 1)) in elves:
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south = True
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west = True
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if north == south == east == west:
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return None
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adjacent: list[Direction] = []
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if north:
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adjacent.append(Direction.North)
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if south:
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adjacent.append(Direction.South)
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if west:
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adjacent.append(Direction.West)
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if east:
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adjacent.append(Direction.East)
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return adjacent
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def has_neighbor(cls, elves: dict[Position, int],
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position: Position, direction: Direction) -> bool:
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match direction:
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case Direction.North:
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return (
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Position(position.x - 1, position.y - 1) in elves
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or Position(position.x, position.y - 1) in elves
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or Position(position.x + 1, position.y - 1) in elves
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)
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case Direction.South:
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return (
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Position(position.x - 1, position.y + 1) in elves
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or Position(position.x, position.y + 1) in elves
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or Position(position.x + 1, position.y + 1) in elves
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)
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case Direction.West:
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return (
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Position(position.x - 1, position.y - 1) in elves
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or Position(position.x - 1, position.y) in elves
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or Position(position.x - 1, position.y + 1) in elves
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)
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case Direction.East:
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return (
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Position(position.x + 1, position.y - 1) in elves
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or Position(position.x + 1, position.y) in elves
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or Position(position.x + 1, position.y + 1) in elves
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)
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def count_empty(self) -> int:
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min_pos, max_pos = self.extent()
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@ -121,6 +102,33 @@ class Ground:
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def extent(self) -> tuple[Position, Position]:
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return Position.component_min(*self.map), Position.component_max(*self.map)
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@classmethod
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def minmax(cls, first: int, second: int) -> tuple[int, int]:
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return (first, second) if first <= second else (second, first)
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@classmethod
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def pair_neighbors(cls, from_pos: Position, to_pos: Position) -> Iterator[Position]:
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if from_pos.x == to_pos.x:
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mn, mx = Ground.minmax(from_pos.y, to_pos.y)
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yield Position(from_pos.x - 1, mn - 1)
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yield Position(from_pos.x, mn - 1)
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yield Position(from_pos.x + 1, mn - 1)
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yield Position(from_pos.x - 1, from_pos.y)
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yield Position(from_pos.x + 1, from_pos.y)
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yield Position(from_pos.x - 1, mx + 1)
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yield Position(from_pos.x, mx + 1)
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yield Position(from_pos.x + 1, mx + 1)
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else:
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mn, mx = Ground.minmax(from_pos.x, to_pos.x)
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yield Position(mn - 1, from_pos.y - 1)
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yield Position(mn - 1, from_pos.y)
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yield Position(mn - 1, from_pos.y + 1)
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yield Position(from_pos.x, from_pos.y - 1)
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yield Position(from_pos.x, from_pos.y + 1)
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yield Position(mx + 1, from_pos.y - 1)
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yield Position(mx + 1, from_pos.y)
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yield Position(mx + 1, from_pos.y + 1)
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def rounds(self, max_rounds: int | None) -> int | None:
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start_dispenser = cycle(iter(Direction))
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if max_rounds is None:
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@ -130,50 +138,54 @@ class Ground:
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elves = {position: 0 for position in self.map}
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min_position, max_position = self.extent()
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for round in it:
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min_position = min_position + Position(-1, -1)
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max_position = max_position + Position(1, 1)
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start = next(start_dispenser)
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proposals: dict[Position, Position] = {}
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for from_pos, last_moved in elves.items():
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if last_moved + 4 < round:
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if not from_pos.is_within(min_position, max_position):
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continue
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touched: set[Position] = set()
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for from_pos, last_touched in elves.items():
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if last_touched + 4 < round:
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continue
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adjacent = self.check_adjacent(elves, from_pos)
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if adjacent is None:
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found = False
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for neighbor in from_pos.all_neighbors():
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if neighbor in elves:
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found = True
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break
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if not found:
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continue
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next_direction = start
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while True:
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if next_direction in adjacent:
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next_direction = next_direction.next()
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else:
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to_pos = next_direction.walk(from_pos)
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if to_pos not in proposals:
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proposals[to_pos] = from_pos
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else:
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del proposals[to_pos]
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found = True
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while Ground.has_neighbor(elves, from_pos, next_direction):
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next_direction = next_direction.next()
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if next_direction == start:
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found = False
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break
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if found:
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to_pos = next_direction.walk(from_pos)
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old_from = proposals.pop(to_pos, None)
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if old_from is None:
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proposals[to_pos] = from_pos
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else:
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touched.add(from_pos)
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touched.add(old_from)
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if not proposals:
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self.map = set(elves)
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return round
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first = True
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for to_pos, from_pos in proposals.items():
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del elves[from_pos]
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elves[to_pos] = round
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del elves[from_pos]
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if first:
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max_position = Position.component_max(to_pos, from_pos)
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min_position = Position.component_min(to_pos, from_pos)
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first = False
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else:
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max_position = Position.component_max(max_position, to_pos, from_pos)
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min_position = Position.component_min(min_position, to_pos, from_pos)
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for neighbor in Ground.pair_neighbors(from_pos, to_pos):
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if neighbor in elves:
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elves[neighbor] = round
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for touched_pos in touched:
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elves[touched_pos] = round
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self.map = set(elves)
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return None
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