最大流Dinic算法模板（pascal）

program rrr(input,output);
const
  inf=123456789;
type
  pointer=^nodetype;
  nodetype=record
     t,c:longint;
     next,rev:pointer;
  end;
var
  a,cur:array[0..10010]of pointer;
  d,q:array[0..10010]of longint;
  p:pointer;
  i,n,m,s,t,c,x,y,ans:longint;
function min(a,b:longint):longint;
begin
   if a<b then exit(a) else exit(b);
end;
procedure add(x,y,c:longint);
begin
   new(p);p^.t:=y;p^.c:=c;p^.next:=a[x];a[x]:=p;
end;
procedure bfs;
var
  h,t:longint;
begin
   for i:=1 to n do d[i]:=-1;
   h:=1;t:=1;q[1]:=s;d[s]:=0;
   while h<=t do
      begin
         p:=a[q[h]];
         while p<>nil do
            begin
               if (d[p^.t]=-1) and (p^.c>0) then
                  begin
                     d[p^.t]:=d[q[h]]+1;
                     inc(t);q[t]:=p^.t;
                  end;
               p:=p^.next;
            end;
         inc(h);
      end;
end;
function dfs(k,f:longint):longint;
var
  ans,r:longint;
  p:pointer;
begin
   if (k=t) or (f=0) then exit(f);
   ans:=0;
   p:=cur[k];
   while p<>nil do
      begin
         if (d[p^.t]=d[k]+1) and (p^.c>0) then
            begin
               r:=dfs(p^.t,min(f,p^.c));
               p^.c:=p^.c-r;
               p^.rev^.c:=p^.rev^.c+r;
               f:=f-r;
               ans:=ans+r;
               if f=0 then break;
            end;
         p:=p^.next;
         cur[k]:=p;
      end;
   if f>0 then d[k]:=-1;
   exit(ans);
end;
begin
   assign(input,'r.in');assign(output,'r.out');reset(input);rewrite(output);
   readln(n,m,s,t);
   for i:=1 to n do a[i]:=nil;
   for i:=1 to m do
      begin
         readln(x,y,c);
         if x=y then continue;
         add(x,y,c);add(y,x,0);
         a[x]^.rev:=a[y];a[y]^.rev:=a[x];
      end;
   ans:=0;
   while true do
      begin
         bfs;
         if d[t]=-1 then break;
         for i:=1 to n do cur[i]:=a[i];
         ans:=ans+dfs(s,inf);
      end;
   write(ans);
   close(input);close(output);
end.