BZOJ1934: [Shoi2007]Vote 善意的投票

  1 const inf=maxlongint;
  2 type node=record
  3      from,go,next,v:longint;
  4      end;
  5 var  tot,i,j,n,m,maxflow,l,r,s,t,x,y:longint;
  6      h,head,q,cur:array[0..1000] of longint;
  7      e:array[0..200000] of node;
  8      function min(x,y:longint):longint;
  9       begin
 10       if x<y then exit(x) else exit(y);
 11       end;
 12 procedure ins(x,y,z:longint);
 13  begin
 14  inc(tot);
 15  e[tot].from:=x;e[tot].go:=y;e[tot].v:=z;e[tot].next:=head[x];head[x]:=tot;
 16  end;
 17 procedure insert(x,y,z:longint);
 18  begin
 19  ins(x,y,z);ins(y,x,0);
 20  end;
 21 function bfs:boolean;
 22  var i,x,y:longint;
 23  begin
 24  fillchar(h,sizeof(h),0);
 25  l:=0;r:=1;q[1]:=s;h[s]:=1;
 26  while l<r do
 27   begin
 28   inc(l);
 29   x:=q[l];
 30   i:=head[x];
 31   while i<>0 do
 32    begin
 33    y:=e[i].go;
 34    if (e[i].v<>0) and (h[y]=0) then
 35     begin
 36      h[y]:=h[x]+1;
 37      inc(r);q[r]:=y;
 38     end;
 39    i:=e[i].next;
 40    end;
 41   end;
 42  exit (h[t]<>0);
 43  end;
 44 function dfs(x,f:longint):longint;
 45  var i,y,used,tmp:longint;
 46  begin
 47  if x=t then exit(f);
 48  used:=0;
 49  i:=cur[x];
 50  while i<>0 do
 51   begin
 52   y:=e[i].go;
 53   if (h[y]=h[x]+1) and (e[i].v<>0) then
 54    begin
 55    tmp:=dfs(y,min(e[i].v,f-used));
 56    dec(e[i].v,tmp);if e[i].v<>0 then cur[x]:=i;
 57    inc(e[i xor 1].v,tmp);
 58    inc(used,tmp);
 59    if used=f then exit(f);
 60    end;
 61   i:=e[i].next;
 62   end;
 63  if used=0 then h[x]:=-1;
 64  exit(used);
 65  end;
 66 procedure dinic;
 67  begin
 68  while bfs do
 69   begin
 70   for i:=s to t do cur[i]:=head[i];
 71   inc(maxflow,dfs(s,inf));
 72   end;
 73  end;
 74 procedure init;
 75  begin
 76  tot:=1;
 77  readln(n,m);
 78  s:=0;t:=n+1;
 79  for i:=1 to n do
 80   begin
 81   read(x);
 82   if x=0 then insert(s,i,1)
 83   else insert(i,t,1);
 84   end;
 85  readln;
 86  for i:=1 to m do begin readln(x,y);insert(x,y,1);insert(y,x,1);end;
 87  end;
 88 procedure main;
 89  begin
 90  maxflow:=0;
 91  dinic;
 92  writeln(maxflow);
 93  end;
 94 begin
 95  assign(input,‘input.txt‘);assign(output,‘output.txt‘);
 96  reset(input);rewrite(output);
 97  init;
 98  main;
 99  close(input);close(output);
100 end.