add enemy cut off trap check

snakes/BestBattleSnake.py

@@ -295,6 +295,15 @@ class BestBattleSnake(TemplateSnake):
       next_options = self._next_turn_option_count(
         future_body, blocked, width, height
       )
+      enemy_safe_options = self._safe_next_turn_option_count(
+        future_body=future_body,
+        other_snakes=other_snakes,
+        food_set=food_set,
+        is_constrictor=is_constrictor,
+        enemy_can_grow_cache=enemy_can_grow_cache,
+        width=width,
+        height=height,
+      )
       territory = self._territory_control_score(
         my_start=point,
         enemy_starts=enemy_heads,
@@ -320,12 +329,17 @@ class BestBattleSnake(TemplateSnake):
       score += reachable_space * 2.6
       score += liberties * 18.0
       score += next_options * 10.0
+      score += enemy_safe_options * 24.0
       score += territory * 0.35
 
       if reachable_space < required_space:
         score -= 1200.0
       if liberties == 0:
         score -= 900.0
+      if enemy_safe_options == 0:
+        score -= 1700.0
+      elif enemy_safe_options == 1:
+        score -= 420.0
 
       enemy_len = enemy_attack_map.get(point)
       if enemy_len is not None:
@@ -382,9 +396,11 @@ class BestBattleSnake(TemplateSnake):
       move_safety[move] = {
         "is_survivable": (not is_dead_end)
         and (not is_losing_head_to_head)
+        and enemy_safe_options > 0
         and health_after_move > 0,
         "reachable_space": reachable_space,
         "next_options": next_options,
+        "enemy_safe_options": enemy_safe_options,
         "tail_escape": has_tail_escape,
       }
 
@@ -474,6 +490,15 @@ class BestBattleSnake(TemplateSnake):
       next_options = self._next_turn_option_count(
         future_body, blocked, width, height
       )
+      enemy_safe_options = self._safe_next_turn_option_count(
+        future_body=future_body,
+        other_snakes=other_snakes,
+        food_set=food_set,
+        is_constrictor=False,
+        enemy_can_grow_cache=enemy_can_grow_cache,
+        width=width,
+        height=height,
+      )
 
       nearest_food_dist = self._nearest_food_distance(point, food_set, blocked, width, height)
       future_tail = future_body[-1]
@@ -507,6 +532,7 @@ class BestBattleSnake(TemplateSnake):
       score += reachable_space * 2.8
       score += liberties * 18.0
       score += next_options * 10.0
+      score += enemy_safe_options * 24.0
       score += territory * 0.50
 
       if likely_dead_end:
@@ -514,6 +540,10 @@ class BestBattleSnake(TemplateSnake):
 
       if losing_head_to_head:
         score -= 1500.0
+      if enemy_safe_options == 0:
+        score -= 1800.0
+      elif enemy_safe_options == 1:
+        score -= 450.0
 
       is_safe_tightening_move = not likely_dead_end and not losing_head_to_head
       if is_safe_tightening_move and enemy_space <= encase_target_space:
@@ -578,8 +608,10 @@ class BestBattleSnake(TemplateSnake):
       move_safety[move] = {
         "is_survivable": (not likely_dead_end)
         and (not losing_head_to_head)
+        and enemy_safe_options > 0
         and health_after_move > 0,
         "reachable_space": reachable_space,
+        "enemy_safe_options": enemy_safe_options,
         "tail_escape": has_tail_escape,
       }
       scores[move] = round(score, 5)
@@ -644,6 +676,15 @@ class BestBattleSnake(TemplateSnake):
       next_options = self._next_turn_option_count(
         future_body, blocked, width, height
       )
+      enemy_safe_options = self._safe_next_turn_option_count(
+        future_body=future_body,
+        other_snakes=other_snakes,
+        food_set=food_set,
+        is_constrictor=True,
+        enemy_can_grow_cache=enemy_can_grow_cache,
+        width=width,
+        height=height,
+      )
       territory = self._territory_control_score(
         my_start=point,
         enemy_starts=enemy_heads,
@@ -669,6 +710,7 @@ class BestBattleSnake(TemplateSnake):
       score += reachable_space * 3.8
       score += liberties * 24.0
       score += next_options * 16.0
+      score += enemy_safe_options * 26.0
       score += territory * 0.65
       score += (reachable_space - enemy_best_space) * 3.2
       score += (max(0, 8 - enemy_total_options)) * 18.0
@@ -685,6 +727,10 @@ class BestBattleSnake(TemplateSnake):
         score -= 2400.0
       elif enemy_len is not None:
         score += 90.0
+      if enemy_safe_options == 0:
+        score -= 2200.0
+      elif enemy_safe_options == 1:
+        score -= 520.0
 
       score -= self._revisit_penalty(point)
 
@@ -698,8 +744,11 @@ class BestBattleSnake(TemplateSnake):
         score -= 35.0
 
       move_safety[move] = {
-        "is_survivable": (not is_dead_end) and (not is_losing_head_to_head),
+        "is_survivable": (not is_dead_end)
+        and (not is_losing_head_to_head)
+        and enemy_safe_options > 0,
         "reachable_space": reachable_space,
+        "enemy_safe_options": enemy_safe_options,
       }
       scores[move] = round(score, 5)
 
@@ -997,6 +1046,64 @@ class BestBattleSnake(TemplateSnake):
       count += 1
     return count
 
+
+  def _safe_next_turn_option_count(self, future_body:list[Coord], other_snakes:list[SnakeState], food_set:set[Point], is_constrictor:bool, enemy_can_grow_cache:dict[Any, bool]|None, width:int, height:int) -> int:
+    """Count next-turn moves that stay safe from enemy head contests."""
+    if not future_body:
+      return 0
+
+    my_len = len(future_body)
+    future_snake = {
+      "head": future_body[0],
+      "body": future_body,
+      "length": my_len,
+    }
+    enemy_attack_map = self._build_enemy_attack_map(
+      my_snake=future_snake,
+      other_snakes=other_snakes,
+      food_set=food_set,
+      is_constrictor=is_constrictor,
+      width=width,
+      height=height,
+      enemy_can_grow_cache=enemy_can_grow_cache,
+    )
+    blocked = self._simulation_blocked(
+      future_body=future_body,
+      other_snakes=other_snakes,
+      food_set=food_set,
+      is_constrictor=is_constrictor,
+      enemy_can_grow_cache=enemy_can_grow_cache,
+    )
+
+    next_head = future_body[0]
+    own_tail = (future_body[-1]["x"], future_body[-1]["y"])
+    own_tail_stacked = self._is_tail_stacked(future_body)
+    safe_count = 0
+
+    for dx, dy in self.DIRECTIONS.values():
+      point = (next_head["x"] + dx, next_head["y"] + dy)
+      if not self._in_bounds(point, width, height):
+        continue
+
+      ate_food = point in food_set
+      can_step_on_tail = self._can_step_on_own_tail(
+        point=point,
+        own_tail=own_tail,
+        own_tail_is_stacked=own_tail_stacked,
+        ate_food=ate_food,
+        is_constrictor=is_constrictor,
+      )
+      if point in blocked and not can_step_on_tail:
+        continue
+
+      enemy_len = enemy_attack_map.get(point)
+      if enemy_len is not None and enemy_len >= my_len:
+        continue
+
+      safe_count += 1
+
+    return safe_count
+
   def _revisit_penalty(self, point:Point) -> float:
     """Return penalty for revisiting recent head positions."""
     if not self.recent_heads:

tests/test_BestBattleSnake.py

@@ -468,6 +468,84 @@ class TestBestBattleSnake(unittest.TestCase):
     move = make_board(game_state).snake_neat_make_a_move()
     self.assertNotEqual(move, "up")
 
+  def test_avoids_enemy_block_in_trap(self):
+    game_state = {
+      "game": {
+        "id": "test-enemy-block-in-trap",
+        "ruleset": {"name": "standard", "version": "v1.0.0"},
+        "source": "custom",
+        "map": "standard",
+      },
+      "turn": 24,
+      "board": {
+        "height": 7,
+        "width": 7,
+        "food": [{"x": 3, "y": 3}],
+        "hazards": [],
+        "snakes": [
+          {
+            "id": "me",
+            "name": "me",
+            "health": 72,
+            "length": 4,
+            "head": {"x": 3, "y": 2},
+            "body": [
+              {"x": 3, "y": 2},
+              {"x": 3, "y": 1},
+              {"x": 2, "y": 1},
+              {"x": 2, "y": 2},
+            ],
+          },
+          {
+            "id": "enemy-a",
+            "name": "enemy-a",
+            "health": 90,
+            "length": 6,
+            "head": {"x": 4, "y": 4},
+            "body": [
+              {"x": 4, "y": 4},
+              {"x": 4, "y": 3},
+              {"x": 4, "y": 2},
+              {"x": 5, "y": 2},
+              {"x": 5, "y": 3},
+              {"x": 5, "y": 4},
+            ],
+          },
+          {
+            "id": "enemy-b",
+            "name": "enemy-b",
+            "health": 90,
+            "length": 6,
+            "head": {"x": 1, "y": 3},
+            "body": [
+              {"x": 1, "y": 3},
+              {"x": 1, "y": 4},
+              {"x": 0, "y": 4},
+              {"x": 0, "y": 3},
+              {"x": 0, "y": 2},
+              {"x": 1, "y": 2},
+            ],
+          },
+        ],
+      },
+      "you": {
+        "id": "me",
+        "name": "me",
+        "health": 72,
+        "length": 4,
+        "head": {"x": 3, "y": 2},
+        "body": [
+          {"x": 3, "y": 2},
+          {"x": 3, "y": 1},
+          {"x": 2, "y": 1},
+          {"x": 2, "y": 2},
+        ],
+      },
+    }
+
+    move = make_board(game_state).snake_neat_make_a_move()
+    self.assertEqual(move, "left")
+
   def test_royale_uses_ruleset_hazard_damage_setting(self):
     game_state = {
       "game": {