吴昊品游戏核心算法 Round 4 (特别篇) —— 贪吃蛇AI
有了模拟算法的基础，在特别篇中，我们可以看下AI了。在GOOGLE公司，每年都有GOOGLE AI CHALLENGE挑战赛，其中就包括国际贪吃蛇AI大赛。但是，由于源码的封闭性，我无法获得了。在网上只有某些70后网友写的“半成品”AI。幸运 地，我联系上了一个北京理工大学的大学生，他做的AI貌似很不错（有单机版和双人模式两种模式可供选择），不过木有源代码，他给出了他自己的QQ以便于 DEBUG。这样子，我正在全力联系那位23岁的大神，目前，只能给出基于“权重”的一种设计思想的AI算法了，虽说是半成品，不过，也是一种思路吧！
文章以及其AI的思想整理如下：
本来去年在写了贪吃蛇之后,就有想要写看AI来耍看的,后来又觉得写起麻烦没想好,没写.
今天又想起了,写来耍看.以前想的要麻烦些,当然可以直接搜索,那个是"可以",但是不太"可行".
//吴昊评注：搜索行不通，便想到了贪心的思想，不考虑全局最优解，根据最短路径（上下左右）+每次（上下左右）被自己“咬死”的可能性局部判断一个操作，贪心出局部最优解
今天上午想的就是求最优解的过程,不过要求最优解要麻烦些.
先以当前状态求到最短路径(需要做一些判断避免咬到自己,和被自己困死),并在每次移动后,地图改变状态后,再以新状态去计算下一步.
那个写起代码就多了,想简单点的几条规则就能达到那种效果.所以就只做当前最优选择,不考虑全局最优解,这样的智能效果应该还可以吧.
那个局部最优解是否可以达到全局最优解,不晓得囊个证明,如果能够达到的话,那工作量就少黑多了.
当前最优选择,按3个步骤:
1.先计算到达目标的,可行的前进方向,上,下,左,右,评估每个方向的权重.
2.计算当前这次移动所产生的影响,然后修正各方向的权重.
3.仲裁选出权重最大的那个方向,作为移动方向.
第2步中,要分解为两个阶段:（考虑两种情况）
1).先判断每个方向移动后,是否会咬到自己,如果是那个方向上的权重设为极小.(解决咬到自己)
2).如果仍一个方向移动后,会和自己接触(形成闭环),需要修正权重避开进入死胡同.(解决困死)
下面是代码：（现在解决了咬到自己，解决困死还没完成，食物在背后还没有完成）
1 // ***************************************************************
2 // LittleAI version: 1.0 ? date: 08/28/2010
3 // -------------------------------------------------------------
4 // File: LittleAI.h
5 // System: Dual-Core T4300 2.10GHz ,DDR2 2GB ,Geforce GT 240M ,
6 // Windows XP SP3 ,MSVC++ 8.0
7 // Author: 风轻炫舞 HoneyCat
8 // Purpose: 贪吃蛇AI
9 // -------------------------------------------------------------
10 // Copyright (C) 2010 - All Rights Reserved
11 // ***************************************************************
12 //
13 // ***************************************************************
14 #ifndef __SNAKEAI_H__
15 #define __SNAKEAI_H__
16 #include "Map.h"
17 #include "Snake.h"
18 #include "Food.h"
19
20 #define DEFAULTWEIGHT 1
21 #define MINWEIGHT -1
22
23 class SnakeAI
24 {
25 struct Action
26 {
27 int _Weight;
28 MoveDir _Dir;
29 };
30
31 public:
32 void Ready(Map& map,Snake& snake,Food& food)
33 {
34
35 }
36
37 void Go(Map& map,Snake& snake,Food& food)
38 {
39 if (snake.IsState(SS_Death))
40 return;
41
42 snake.ChangDir(Decision(map,snake,food));
43 }
44
45 MoveDir Decision(Map& map,Snake& snake,Food& food)
46 {
47 Action nextact[4];
48 memset(nextact,0x0,sizeof(nextact));
49 int actnum=4;
50
51 CalcFeasibleAct(nextact,actnum,map,snake,food);
52 NextActEffect(nextact,actnum,map,snake,food);
53
54 return Arbitration(nextact,actnum,snake);
55 }
56
57 protected:
58
59 void NextActEffect(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
60 {
61 if (NoBiteSelf(nextact,actnum,map,snake,food))
62 NoBesiegeSelf(nextact,actnum,map,snake,food);
63 }
64
65 void CalcFeasibleAct(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
66 {
67 InitAction(nextact,actnum,snake);
68 CalcWeight(nextact,actnum,snake,food);
69 }
70
71 void InitAction(Action* nextact,int& actnum,Snake& snake)
72 {
73 actnum=4;
74 nextact[snake.GetDir()]._Weight=DEFAULTWEIGHT; nextact[snake.GetDir()]._Dir=snake.GetDir();
75 nextact[snake.GetLeftDir()]._Weight=0; nextact[snake.GetLeftDir()]._Dir=snake.GetLeftDir();
76 nextact[snake.GetRightDir()]._Weight=0; nextact[snake.GetRightDir()]._Dir=snake.GetRightDir();
77 nextact[snake.GetBackDir()]._Weight=MINWEIGHT; nextact[snake.GetBackDir()]._Dir=snake.GetBackDir();
78 }
79
80 void CalcWeight(Action* nextact,int& actnum,Snake& snake,Food& food)
81 {
82 if (food.IsState(FS_Eaten))
83 {
84 return;
85 }
86 MapPoint curpos=snake.GetBody(snake.GetHead());
87 MapPoint dest=food.GetPos();
88
89 int len=abs(dest._X-curpos._X)+abs(dest._Y-curpos._Y);
90
91 if ((dest._X-curpos._X)>0)
92 {
93 nextact[MD_RIGHT]._Weight=len;
94 }
95 else if ((dest._X-curpos._X)<0)
96 {
97 nextact[MD_LEFT]._Weight=len;
98 }
99 else
100 {
101 nextact[MD_RIGHT]._Weight=0;
102 nextact[MD_LEFT]._Weight=0;
103 }
104
105 if ((dest._Y-curpos._Y)>0)
106 {
107 nextact[MD_UP]._Weight=len;
108 }
109 else if ((dest._Y-curpos._Y)<0)
110 {
111 nextact[MD_DOWN]._Weight=len;
112 }
113 else if ((dest._Y-curpos._Y)==0)
114 {
115 nextact[MD_UP]._Weight=0;
116 nextact[MD_DOWN]._Weight=0;
117 }
118 }
119
120 bool NoBiteSelf(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
121 {
122 MapPoint headpos=snake.GetBody(snake.GetHead());
123 MapPoint tailpos=snake.GetBody(snake.GetTail());
124 MapPoint dirpos;
125 bool touchself=false;
126 for (int i=0;i<actnum;++i)
127 {
128 NextHeadPos(dirpos,headpos,nextact[i]);
129 if (map.WhatInMap(dirpos._X,dirpos._Y)==OT_Snake)
130 {
131 if (dirpos._X==tailpos._X&&dirpos._Y==tailpos._Y)
132 continue;
133
134 nextact[i]._Weight=MINWEIGHT;
135 touchself=true;
136 }
137 }
138 return touchself;
139 }
140
141 void NextHeadPos(MapPoint& pos,MapPoint& curpos,Action& nextact)
142 {
143 switch(nextact._Dir)
144 {
145 case MD_DOWN:
146 case MD_UP:
147 pos._X=curpos._X;
148 pos._Y=curpos._Y+(nextact._Dir<<1)-1;
149 break;
150 case MD_LEFT:
151 case MD_RIGHT:
152 pos._X=curpos._X+((nextact._Dir-MD_LEFT)<<1)-1;
153 pos._Y=curpos._Y;
154 break;
155 }
156 };
157
158 void NoBesiegeSelf(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
159 {
160
161 }
162
163 MoveDir Arbitration(Action* nextact,int actnum,Snake& snake)
164 {
165 Action act;
166 act._Weight=MINWEIGHT;
167 for (int i=0;i<actnum;++i)
168 {
169 if (act._Weight<nextact[i]._Weight)
170 {
171 act=nextact[i];
172 }
173 }
174 LogAct(act);
175 return act._Dir;
176 }
177
178 void LogAct(Action& act)
179 {
180 switch (act._Dir)
181 {
182 case MD_UP:
183 printf("Move Up/n");
184 break;
185 case MD_DOWN:
186 printf("Move Down/n");
187 break;
188 case MD_LEFT:
189 printf("Move Left/n");
190 break;
191 case MD_RIGHT:
192 printf("Move Right/n");
193 break;
194 }
195 }
196
197 };
198
199 #endif __SNAKEAI_H__
200
201
2 // LittleAI version: 1.0 ? date: 08/28/2010
3 // -------------------------------------------------------------
4 // File: LittleAI.h
5 // System: Dual-Core T4300 2.10GHz ,DDR2 2GB ,Geforce GT 240M ,
6 // Windows XP SP3 ,MSVC++ 8.0
7 // Author: 风轻炫舞 HoneyCat
8 // Purpose: 贪吃蛇AI
9 // -------------------------------------------------------------
10 // Copyright (C) 2010 - All Rights Reserved
11 // ***************************************************************
12 //
13 // ***************************************************************
14 #ifndef __SNAKEAI_H__
15 #define __SNAKEAI_H__
16 #include "Map.h"
17 #include "Snake.h"
18 #include "Food.h"
19
20 #define DEFAULTWEIGHT 1
21 #define MINWEIGHT -1
22
23 class SnakeAI
24 {
25 struct Action
26 {
27 int _Weight;
28 MoveDir _Dir;
29 };
30
31 public:
32 void Ready(Map& map,Snake& snake,Food& food)
33 {
34
35 }
36
37 void Go(Map& map,Snake& snake,Food& food)
38 {
39 if (snake.IsState(SS_Death))
40 return;
41
42 snake.ChangDir(Decision(map,snake,food));
43 }
44
45 MoveDir Decision(Map& map,Snake& snake,Food& food)
46 {
47 Action nextact[4];
48 memset(nextact,0x0,sizeof(nextact));
49 int actnum=4;
50
51 CalcFeasibleAct(nextact,actnum,map,snake,food);
52 NextActEffect(nextact,actnum,map,snake,food);
53
54 return Arbitration(nextact,actnum,snake);
55 }
56
57 protected:
58
59 void NextActEffect(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
60 {
61 if (NoBiteSelf(nextact,actnum,map,snake,food))
62 NoBesiegeSelf(nextact,actnum,map,snake,food);
63 }
64
65 void CalcFeasibleAct(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
66 {
67 InitAction(nextact,actnum,snake);
68 CalcWeight(nextact,actnum,snake,food);
69 }
70
71 void InitAction(Action* nextact,int& actnum,Snake& snake)
72 {
73 actnum=4;
74 nextact[snake.GetDir()]._Weight=DEFAULTWEIGHT; nextact[snake.GetDir()]._Dir=snake.GetDir();
75 nextact[snake.GetLeftDir()]._Weight=0; nextact[snake.GetLeftDir()]._Dir=snake.GetLeftDir();
76 nextact[snake.GetRightDir()]._Weight=0; nextact[snake.GetRightDir()]._Dir=snake.GetRightDir();
77 nextact[snake.GetBackDir()]._Weight=MINWEIGHT; nextact[snake.GetBackDir()]._Dir=snake.GetBackDir();
78 }
79
80 void CalcWeight(Action* nextact,int& actnum,Snake& snake,Food& food)
81 {
82 if (food.IsState(FS_Eaten))
83 {
84 return;
85 }
86 MapPoint curpos=snake.GetBody(snake.GetHead());
87 MapPoint dest=food.GetPos();
88
89 int len=abs(dest._X-curpos._X)+abs(dest._Y-curpos._Y);
90
91 if ((dest._X-curpos._X)>0)
92 {
93 nextact[MD_RIGHT]._Weight=len;
94 }
95 else if ((dest._X-curpos._X)<0)
96 {
97 nextact[MD_LEFT]._Weight=len;
98 }
99 else
100 {
101 nextact[MD_RIGHT]._Weight=0;
102 nextact[MD_LEFT]._Weight=0;
103 }
104
105 if ((dest._Y-curpos._Y)>0)
106 {
107 nextact[MD_UP]._Weight=len;
108 }
109 else if ((dest._Y-curpos._Y)<0)
110 {
111 nextact[MD_DOWN]._Weight=len;
112 }
113 else if ((dest._Y-curpos._Y)==0)
114 {
115 nextact[MD_UP]._Weight=0;
116 nextact[MD_DOWN]._Weight=0;
117 }
118 }
119
120 bool NoBiteSelf(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
121 {
122 MapPoint headpos=snake.GetBody(snake.GetHead());
123 MapPoint tailpos=snake.GetBody(snake.GetTail());
124 MapPoint dirpos;
125 bool touchself=false;
126 for (int i=0;i<actnum;++i)
127 {
128 NextHeadPos(dirpos,headpos,nextact[i]);
129 if (map.WhatInMap(dirpos._X,dirpos._Y)==OT_Snake)
130 {
131 if (dirpos._X==tailpos._X&&dirpos._Y==tailpos._Y)
132 continue;
133
134 nextact[i]._Weight=MINWEIGHT;
135 touchself=true;
136 }
137 }
138 return touchself;
139 }
140
141 void NextHeadPos(MapPoint& pos,MapPoint& curpos,Action& nextact)
142 {
143 switch(nextact._Dir)
144 {
145 case MD_DOWN:
146 case MD_UP:
147 pos._X=curpos._X;
148 pos._Y=curpos._Y+(nextact._Dir<<1)-1;
149 break;
150 case MD_LEFT:
151 case MD_RIGHT:
152 pos._X=curpos._X+((nextact._Dir-MD_LEFT)<<1)-1;
153 pos._Y=curpos._Y;
154 break;
155 }
156 };
157
158 void NoBesiegeSelf(Action* nextact,int& actnum,Map& map,Snake& snake,Food& food)
159 {
160
161 }
162
163 MoveDir Arbitration(Action* nextact,int actnum,Snake& snake)
164 {
165 Action act;
166 act._Weight=MINWEIGHT;
167 for (int i=0;i<actnum;++i)
168 {
169 if (act._Weight<nextact[i]._Weight)
170 {
171 act=nextact[i];
172 }
173 }
174 LogAct(act);
175 return act._Dir;
176 }
177
178 void LogAct(Action& act)
179 {
180 switch (act._Dir)
181 {
182 case MD_UP:
183 printf("Move Up/n");
184 break;
185 case MD_DOWN:
186 printf("Move Down/n");
187 break;
188 case MD_LEFT:
189 printf("Move Left/n");
190 break;
191 case MD_RIGHT:
192 printf("Move Right/n");
193 break;
194 }
195 }
196
197 };
198
199 #endif __SNAKEAI_H__
200
201
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