3396: [Usaco2009 Jan]Total flow 水流

3396: [Usaco2009 Jan]Total flow 水流

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

3

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。。

type
    point=^node;
    node=record
               g,w:longint;
               next,anti:point;
    end;
var
   i,j,k,l,m,n,ans,s,t:longint;
   a:array[0..100] of point;
   d,dv:array[0..100] of longint;
   c1,c2,c3:char;
function min(x,y:longint):longint;inline;
         begin
              if x<y then min:=x else min:=y;
         end;
procedure add(x,y,z:longint);inline;
          var p:point;
          begin
               new(p);p^.g:=y;p^.w:=z;p^.next:=a[x];a[x]:=p;
               new(p);p^.g:=x;p^.w:=0;p^.next:=a[y];a[y]:=p;
               a[y]^.anti:=a[x];a[x]^.anti:=a[y];
          end;
function dfs(x,flow:longint):longint;inline;
         var p:point;k:longint;
         begin
              if x=t then exit(flow);
              dfs:=0;p:=a[x];
              while p<>nil do
                    begin
                         if (P^.w>0) and (d[x]=(d[p^.g]+1)) then
                            begin
                                 k:=dfs(p^.g,min(p^.w,flow-dfs));
                                 dec(p^.w,k);
                                 inc(p^.anti^.w,k);
                                 inc(dfs,k);
                                 if dfs=flow then exit;
                            end;
                         p:=p^.next;
                    end;
              if d[s]=n then exit;
              dec(dv[d[x]]);
              if dv[d[x]]=0 then d[s]:=n;
              inc(d[x]);
              inc(dv[d[x]]);
         end;
function trans(x:char):longint;inline;
         begin
              case x of
                   'A'..'Z':exit(ord(x)-ord('A')+1);
                   'a'..'z':exit(ord(x)-ord('a')+27);
              end;
         end;
function getc:longint;inline;
         begin
              repeat
                    read(c1);
              until (upcase(c1)>='A') and (upcase(c1)<='Z');
              exit(trans(c1));
         end;
begin
     readln(m);n:=52;
     for i:=1 to n do a[i]:=nil;
     s:=1;t:=26;
     for i:=1 to m do
         begin
              j:=getc;k:=getc;readln(l);
              add(j,k,l);
         end;
     fillchar(d,sizeof(d),0);
     fillchar(dv,sizeof(dv),0);
     dv[0]:=n;
     ans:=0;
     while d[s]<n do inc(ans,dfs(s,maxlongint));
     writeln(ans);
end.