HDU 2605 Snake（DFS+BFS+技巧+细节）（好题）
SnakeTime Limit: 10000/6000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 222 Accepted Submission(s): 45
Problem Description
Snake is a popular game , and I believe most of us had played it . The Original game is that you can control a snake to eat the magic bean and after the snake eat one magic bean , the length of the snake’s body will get longer .But today we are talking about a new game. These are the rules of the new Snake Game :
1. The length of the snake’s body won’t change even though it eat a magic bean. 2. Some pairs of the beans have a relation , that is, one of them can not be eaten until another one had been eaten . We call the latter “the key bean” . For example , if A can’t be eaten until B had been eaten ,we say “B is the key bean of A”. (That means when A can’t be eaten , the snake can not move into the grid where A is.) 3. The snake could not move to a wall or its body.Befor it move,it will chooses an adjacent vacant square of its head,which is neither a stone nor occupied by its body. 
Input
The first line contain a integer T (T <= 10).Followed by T cases. Each case contain five parts.
The first part: six integers ,H,W,L,K,R,N,(H <= 20 , W <= 20 , L <= 8 , K <= 7 ) means the height of the map , the width of the map , the length of the snake’s body, the number of the magic beans . the number of the relations , the number of the wall respectively. The second part: L lines , each line contain two integer h i ,w i, indicating the original position of each block of snake's body, from B 1(h 1,w 1) to B L(h L,w L) orderly, where 1<=h i<=H, and 1<=w i<=W,1<=i<=L. The third part: K lines ,each line contain two integer h i ,w i , indicating the position of each magic bean , from MB 1(h 1,w 1) to MB K(h K,w K) orderly, where 1<=h i<=H, and 1<=w i<=W,1<=i<=K. The fourth part : R lines , each line contain two integer A ,B means “A is the key bean of B ”. The A and B may appear several times , but “one bean will have only one key bean”. The fifth part: N lines , each line contain two integer h i ,w i , indicating the position of each wall , from W 1(h 1,w 1) to W N(h N,w N) orderly, where 1<=h i<=H, and 1<=w i<=W,1<=i<=N.
Output
For each case , if the snake could eat all the magic beans , output the minimum step it took. If the snake could not , just output “-1” (without the quotation marks) .
Sample Input
1 8 9 5 2 1 8 5 2 6 2 6 3 6 4 6 5 4 2 2 6 2 1 2 5 3 5 4 4 4 5 4 6 5 6 5 7 6 7
Sample Output
21
Author
Teddy
Source
HDU 1st “Vegetable-Birds Cup” Programming Open Contest
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题解：
这是个好题啊。贪食蛇。爆搜。
注意一下一些细节和技巧就可以。
可能需要你花很多时间慢慢写....
反正我写了一个晚上....
很考验自己的的代码能力，我写了7K...300+行...
注意：
豆子也要成环...dfs判断一下即可。
然后再BFS，判断是否越界或者撞墙，还要判断豆子能不能吃。还要判断蛇头不能碰到自己。
注意MLE，利用一下位运算就可以了。用bitset大法应该也是可以的。
