1339 / 1163: [Baltic2008]Mafia

 1 /**************************************************************
 2     Problem: 1163
 3     User: HansBug
 4     Language: Pascal
 5     Result: Accepted
 6     Time:156 ms
 7     Memory:2652 kb
 8 ****************************************************************/
 9  
10 type
11     point=^node;
12     node=record
13                g,w:longint;
14                next,anti:point;
15     end;
16 var
17    i,j,k,l,m,n,s,t,ans:longint;
18    a:array[0..5000] of point;
19    d,dv:array[0..5000] of longint;
20 function min(x,y:longint):longint;
21          begin
22               if x<y then min:=x else min:=y;
23          end;
24 procedure add(x,y,z:longint);
25           var p:point;
26           begin
27                new(p);p^.g:=y;p^.w:=z;p^.next:=a[x];a[x]:=p;
28                new(p);p^.g:=x;p^.w:=0;p^.next:=a[y];a[y]:=p;
29                a[x]^.anti:=a[y];a[y]^.anti:=a[x];
30           end;
31 function dfs(x,flow:longint):longint;
32          var p:point;k:longint;
33          begin
34               if x=t then exit(flow);
35               dfs:=0;p:=a[x];
36               while p<>nil do
37                     begin
38                          if (p^.w<>0) and (d[x]=(d[p^.g]+1)) then
39                             begin
40                                  k:=dfs(p^.g,min(flow-dfs,p^.w));
41                                  if p^.w<>maxlongint then dec(p^.w,k);
42                                  if p^.anti^.w<>maxlongint then inc(p^.anti^.w,k);
43                                  inc(dfs,k);if dfs=flow then exit;
44                             end;
45                          p:=p^.next;
46                     end;
47               if d[s]=n then exit;
48               dec(dv[d[x]]);
49               if dv[d[x]]=0 then d[s]:=n;
50               inc(d[x]);inc(dv[d[x]]);
51          end;
52 begin
53      readln(n,m);
54      for i:=1 to n*2 do a[i]:=nil;
55      readln(s,t);s:=s*2-1;t:=t*2;
56      for i:=1 to n do
57          begin
58               readln(j);
59               add(i*2-1,i*2,j);
60          end;
61      for i:=1 to m do
62          begin
63               readln(j,k);
64               add(j*2,k*2-1,maxlongint);
65               add(k*2,j*2-1,maxlongint);
66          end;
67      fillchar(dv,sizeof(dv),0);
68      fillchar(d,sizeof(d),0);
69      ans:=0;n:=n*2;
70      while d[s]<n do inc(ans,dfs(s,maxlongint));
71      writeln(ans);
72      readln;
73 end.