dinic板子

procedure dinic;
begin
  while bfs do inc(ans,dfs(s,maxlongint));
end;

function bfs:boolean;
var h,tail,i,j:longint;
begin
  fillchar(dis,sizeof(dis),$3f);
  h:=0;tail:=1;l[1]:=s;dis[s]:=0;
  while h<>tail do
  begin
    inc(h);i:=l[h];j:=head[i];
    while j>0 do
    begin
      if(dis[i]+1<dis[q[j]])and(flow[j]>0) then
      begin
        inc(tail);l[tail]:=q[j];
        dis[q[j]]:=dis[i]+1;
      end;
      j:=next[j];
    end;
  end;
  if dis[t]=$3f3f3f3f then exit(false) else exit(true);
end;

function dfs(i,ll:longint):longint;
var j,tmp,x:longint;
begin
  if i=t then exit(ll);
  j:=head[i];x:=0;
  while j>0 do
  begin
    if(flow[j]>0)and(dis[q[j]]=dis[i]+1) then
    begin
      tmp:=dfs(q[j],min(ll-x,flow[j]));
      dec(flow[j],tmp);
      inc(flow[j xor 1],tmp);
      inc(x,tmp);
      if x=ll then exit(ll);
    end;
    j:=next[j];
  end;
  if x=0 then dis[i]:=-1;
  exit(x);
end;