拯救ice-cream（Vijos p1340)

　　今晚我和几个哥们一起编这道坑爹的搜索题，BFS，刚开始总是溢出，绞尽脑汁想了各种优化办法。

　　刚开始直接用bool判重，后来发现这样判重可能会漏掉最优解。拿了水出来的60分后，没编了，王大牛还在奋斗，我们商讨了一下判重方法，用一个记录，记录目前到这点的最短时间，这样就可以避免漏掉最优解的情况，以下是借用王大牛的程序：

　　

 1 program P1340;
 2 type
 3         rec=record
 4                 x,y:longint;
 5                 di:longint;
 6                 time:longint;
 7         end;
 8 var
 9         s:array[1..100000,1..4] of longint;
10         time:array[1..30,1..30] of longint;
11         a:array[1..30,1..30] of char;
12         sb1,sb2:char;
13         b:array[1..30,1..30] of longint;
14         q,open,closed,t,x,y,x0,y0,x1,y1,i,j,k,l,m:longint;
15 begin
16         q:=maxlongint;
17         assign(input,'haha.in');
18         reset(input);
19         readln(t);
20         read(x,y);
21         for j:=1 to y do
22                 begin
23                 read(sb1,sb2);
24                  for i:=1 to x do
25                         begin
26                                 read(a[i,j]);
27                                 if a[i,j]='.'then b[i,j]:=1
28                                         else if a[i,j]='#'then b[i,j]:=2
29                                                 else if a[i,j]='o' then b[i,j]:=maxlongint
30                                                         else if a[i,j]='s' then begin x0:=i;y0:=j; b[i,j]:=1;end
31                                                         else if a[i,j]='m' then begin x1:=i;y1:=j; b[i,j]:=0;end;
32                         end;
33                  end;
34         close(input);
35         for j:=1 to y do
36                 for i:=1 to x do
37                         time[i,j]:=maxlongint;
38         closed:=0; open:=1;
39         s[1,1]:=x0; s[1,2]:=y0; s[1,3]:=0; s[1,4]:=0;
40         repeat
41         repeat
42                 inc(closed);
43                 if time[s[closed,1],s[closed,2]]>s[closed,4] then begin
44                 time[s[closed,1],s[closed,2]]:=s[closed,4];
45                 if (s[closed,3]<>1)and(s[closed,1]<x)and(a[s[closed,1]+1,s[closed,2]]<>'o')then begin
46                                                                 inc(open);
47                                                                 s[open,1]:=s[closed,1]+1;
48                                                                 s[open,2]:=s[closed,2];
49                                                                 s[open,3]:=3;
50                                                                 s[open,4]:=s[closed,4]+b[s[closed,1],s[closed,2]];
51                                                                 end;
52                                                                 if a[s[open,1],s[open,2]]='m' then break;
53                 if (s[closed,3]<>3)and(s[closed,1]>1)and(a[s[closed,1]-1,s[closed,2]]<>'o') then begin
54                                                                 inc(open);
55                                                                 s[open,1]:=s[closed,1]-1;
56                                                                 s[open,2]:=s[closed,2];
57                                                                 s[open,3]:=1;
58                                                                 s[open,4]:=s[closed,4]+b[s[closed,1],s[closed,2]];
59                                                                 end;
60                                                                 if a[s[open,1],s[open,2]]='m' then break;
61                 if (s[closed,3]<>0)and(s[closed,2]>1)and(a[s[closed,1],s[closed,2]-1]<>'o') then begin
62                                                                 inc(open);
63                                                                 s[open,1]:=s[closed,1];
64                                                                 s[open,2]:=s[closed,2]-1;
65                                                                  s[open,3]:=2;
66                                                                 s[open,4]:=s[closed,4]+b[s[closed,1],s[closed,2]];
67                                                                 end;
68                                                                 if a[s[open,1],s[open,2]]='m' then break;
69                 if (s[closed,3]<>2)and(s[closed,2]<y)and(a[s[closed,1],s[closed,2]+1]<>'o') then begin
70                                                                 inc(open);
71                                                                 s[open,1]:=s[closed,1];
72                                                                 s[open,2]:=s[closed,2]+1;
73                                                                 s[open,3]:=0;
74                                                                 s[open,4]:=s[closed,4]+b[s[closed,1],s[closed,2]];
75                                                                 end;
76                                                                 if a[s[open,1],s[open,2]]='m' then break;
77                 end;
78         until (a[s[open,1],s[open,2]]='m')or(closed=open);
79         if q>s[open,4] then q:=s[open,4];
80         until (closed=open);
81         if q>=t then write('55555')
82         else
83         write(q);
84 end.

 

　　大概就是BFS，然后判重，没什么别的技巧，憋了几个小时总算是憋出了100分，惭愧啊惭愧！

 

　　By ZYT

　　12.10.05

posted @ 2012-10-05 22:04  何如薄幸锦衣郎  阅读(285)  评论(0)  编辑  收藏  举报