3396: [Usaco2009 Jan]Total flow 水流

Time Limit: 1 Sec Memory Limit: 128 MB
Submit: 179 Solved: 73
[Submit][Status]

Description

Input

第1行输入N，之后N行每行描述一条水管，前两个英文字母表示水管的两端（大小写字母是不一样的），后一个整数表示水管的流量，流量不会超过1000.

Output

一个整数，表示总流量．

Sample Input

5
A B 3
B C 3
C D 5
D Z 4
B Z 6

Sample Output

HINT

Source

Silver

题解：WA了6次再读题才发现大小写字母不一样TT。别的没了，直接上sap模板A之。。

 1 type
 2     point=^node;
 3     node=record
 4                g,w:longint;
 5                next,anti:point;
 6     end;
 7 var
 8    i,j,k,l,m,n,ans,s,t:longint;
 9    a:array[0..100] of point;
10    d,dv:array[0..100] of longint;
11    c1,c2,c3:char;
12 function min(x,y:longint):longint;inline;
13          begin
14               if x<y then min:=x else min:=y;
15          end;
16 procedure add(x,y,z:longint);inline;
17           var p:point;
18           begin
19                new(p);p^.g:=y;p^.w:=z;p^.next:=a[x];a[x]:=p;
20                new(p);p^.g:=x;p^.w:=0;p^.next:=a[y];a[y]:=p;
21                a[y]^.anti:=a[x];a[x]^.anti:=a[y];
22           end;
23 function dfs(x,flow:longint):longint;inline;
24          var p:point;k:longint;
25          begin
26               if x=t then exit(flow);
27               dfs:=0;p:=a[x];
28               while p<>nil do
29                     begin
30                          if (P^.w>0) and (d[x]=(d[p^.g]+1)) then
31                             begin
32                                  k:=dfs(p^.g,min(p^.w,flow-dfs));
33                                  dec(p^.w,k);
34                                  inc(p^.anti^.w,k);
35                                  inc(dfs,k);
36                                  if dfs=flow then exit;
37                             end;
38                          p:=p^.next;
39                     end;
40               if d[s]=n then exit;
41               dec(dv[d[x]]);
42               if dv[d[x]]=0 then d[s]:=n;
43               inc(d[x]);
44               inc(dv[d[x]]);
45          end;
46 function trans(x:char):longint;inline;
47          begin
48               case x of
49                    'A'..'Z':exit(ord(x)-ord('A')+1);
50                    'a'..'z':exit(ord(x)-ord('a')+27);
51               end;
52          end;
53 function getc:longint;inline;
54          begin
55               repeat
56                     read(c1);
57               until (upcase(c1)>='A') and (upcase(c1)<='Z');
58               exit(trans(c1));
59          end;
60 begin
61      readln(m);n:=52;
62      for i:=1 to n do a[i]:=nil;
63      s:=1;t:=26;
64      for i:=1 to m do
65          begin
66               j:=getc;k:=getc;readln(l);
67               add(j,k,l);
68          end;
69      fillchar(d,sizeof(d),0);
70      fillchar(dv,sizeof(dv),0);
71      dv[0]:=n;
72      ans:=0;
73      while d[s]<n do inc(ans,dfs(s,maxlongint));
74      writeln(ans);
75 end.