最大流Dinic算法模板（pascal）

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