Strategická: Pathfinding

klient/play.py

@@ -1,7 +1,8 @@
 #!/usr/bin/env python3
 from __future__ import annotations
 from enum import Enum
-from typing import Callable, Iterable, List, Optional
+from typing import Callable, Iterable, Optional, List, Set
+import collections
 import json
 import sys
 
@@ -13,6 +14,17 @@ class Action(Enum):
     RIGHT = "right"
     STAY = None
 
+    def invert(self) -> Action:
+        if self == Action.UP:
+            return Action.DOWN
+        if self == Action.DOWN:
+            return Action.UP
+        if self == Action.LEFT:
+            return Action.RIGHT
+        if self == Action.RIGHT:
+            return Action.LEFT
+        return Action.STAY
+
 
 class State:
     def __init__(self, state: dict) -> None:
@@ -44,6 +56,12 @@ class Field:
         self.home_for_team = home_for_team
         self.occupied_by_team = occupied_by_team
 
+    def __eq__(self, other: Field) -> bool:
+        return (self.i, self.j) == (other.i, other.j)
+
+    def __hash__(self) -> int:
+        return hash((self.i, self.j))
+
     def get_neighbour_field(self, action: Action) -> Field:
         if action == Action.UP:
             neighbour_i = self.i - 1
@@ -111,6 +129,31 @@ def find_team_members(team_id: int) -> List[Member]:
     return result
 
 
+def pathfind(member: Member, goal: Field) -> Action:
+    """Find the shortest path from member position to goal.
+
+    Returns the first action to take.
+    If there is no path, returns Action.STAY.
+    """
+
+    # BFS from goal to member
+    # this direction makes it easier to realize that no path exists
+    explored: Set[Field] = set()
+    queue = collections.deque([goal])
+    while queue:
+        field = queue.popleft()
+        for action in Action:
+            neighbour = field.get_neighbour_field(action)
+            if (neighbour in explored or
+                not neighbour.is_accessible(member.team)):
+                continue
+            if field == member.field:
+                return action.invert()
+            queue.append(neighbour)
+            explored.add(field)
+    return Action.STAY
+
+
 def build_turn(members: Iterable[Member]) -> dict:
     return {
         "members": [