項目說明：https://inst.eecs.berkeley.edu/~cs61a/sp21/proj/ants/
螞蟻大戰蜜蜂 靈感來源：植物大戰僵屍（Plants Vs. Zombies，PVZ）
Phase 1： https://www.cnblogs.com/ikventure/p/14986805.html
Phase 2： https://www.cnblogs.com/ikventure/p/14988467.html
Phase 3： https://www.cnblogs.com/ikventure/p/14992754.html
Phase 4： https://www.cnblogs.com/ikventure/p/14994734.html
效果展示： https://www.cnblogs.com/ikventure/p/15001093.html
游戲說明
游戲按輪次進行，每一輪中，新的蜜蜂都可能進入蟻群領地。然后，放置新的螞蟻來保衛它們的領地。 最后，所有昆蟲（螞蟻，蜜蜂）都會采取單獨的行動。蜜蜂沿着tunnel從右往左移動，遇到螞蟻則攻擊螞蟻。不同類型的螞蟻執行不同的動作，例如收集更多食物或向蜜蜂扔樹葉。 當一只蜜蜂到達tunnel盡頭或者摧毀了 QueenAnt（如果存在），你就輸了；整個蜜蜂艦隊都被打敗，你就贏了；游戲結束。
核心概念和核心類都跟PVZ類似。
Phase 1: Basic gameplay
Problem 1 (1 pt)
Part A: 當前放置任一類型Ant都沒有cost，基類Ant的food_cost為0。任務：根據表格的"Food cost"重寫HarvesterAnt和ThrowerAnt的類屬性。
| Class | Food Cost | Initial Health |
|---|---|---|
| HarvesterAnt | 2 | 1 |
| ThrowerAnt | 3 | 1 |
Part B: 放置ant需要消耗食物，HarvesterAnt生產食物（類似PVZ向日葵） 任務：完成HarvesterAnt action方法。
代碼：
class HarvesterAnt(Ant):
"""HarvesterAnt produces 1 additional food per turn for the colony."""
name = 'Harvester'
implemented = True
# OVERRIDE CLASS ATTRIBUTES HERE
food_cost = 2
def action(self, gamestate):
"""Produce 1 additional food for the colony.
gamestate -- The GameState, used to access game state information.
"""
# BEGIN Problem 1
"*** YOUR CODE HERE ***"
gamestate.food += 1
# END Problem 1
class ThrowerAnt(Ant):
"""ThrowerAnt throws a leaf each turn at the nearest Bee in its range."""
name = 'Thrower'
implemented = True
damage = 1
# ADD/OVERRIDE CLASS ATTRIBUTES HERE
food_cost = 3
Problem 2 (2 pt)
任務：完成 Place.__init__記錄入口entrance。
分析：類似鏈表結構，創建Place對象時，entrance為None；如果這個對象的exit不為None，將這個exit的entrance設置為這個對象。
代碼：
class Place:
"""A Place holds insects and has an exit to another Place."""
def __init__(self, name, exit=None):
"""Create a Place with the given NAME and EXIT.
name -- A string; the name of this Place.
exit -- The Place reached by exiting this Place (may be None).
"""
self.name = name
self.exit = exit
self.bees = [] # A list of Bees
self.ant = None # An Ant
self.entrance = None # A Place
# Phase 1: Add an entrance to the exit
# BEGIN Problem 2
"*** YOUR CODE HERE ***"
if self.exit:
self.exit.entrance = self
# END Problem 2
Problem 3 (2 pt)
ThrowerAnt類似豌豆射手，需要根據nearest_bee方法確定攻擊哪只蜜蜂(攻擊身前且不在蜂巢中的蜜蜂)。
任務：修改nearest_bee讓它返回最近的蜜蜂之一。
- 從豌豆射手ThrowerAnt的位置開始
- 對於每個place，如果其中有蜜蜂，則隨機返回蜜蜂之一；如果沒有蜜蜂，查找更前面的place
- 如果沒有蜜蜂可以攻擊，返回None
遍歷豌豆射手身前的place時，由於self.place不會變，所以引入新參數next_place，place中沒有蜜蜂，則賦值為下一個格子next_place.entrance，直到找到有蜜蜂的place或者到達蜂巢。
注意：phase 2中problem 4有新要求，要考慮ant的攻擊距離，相應的problem 3部分會在phase 2進行修改。
class ThrowerAnt(Ant):
"""ThrowerAnt throws a leaf each turn at the nearest Bee in its range."""
name = 'Thrower'
implemented = True
damage = 1
# ADD/OVERRIDE CLASS ATTRIBUTES HERE
food_cost = 3
def nearest_bee(self, beehive):
"""Return the nearest Bee in a Place that is not the HIVE (beehive), connected to
the ThrowerAnt's Place by following entrances.
This method returns None if there is no such Bee (or none in range).
"""
# BEGIN Problem 3 and 4
# 不能改變ant的位置self.place
next_place = self.place
while not next_place.is_hive():
if next_place.bees:
return bee_selector(next_place.bees) # REPLACE THIS LINE
next_place = next_place.entrance
return None
# END Problem 3 and 4