[NOI 2006] 最大获利 80分

最后两点怎么搞都要30s+，但是我不会什么优化啊…暂时就这样吧。Dinic的时间复杂度是O(N^2*M)

这题和TDL的幼儿园模板是一样的。

这次写网络流给自己计时了，大约是40min左右，后来都跑去倒腾后面两组数据去了…

program profit;
type ptype=^node;
     node=record
            v,w,flow:longint;
            next:ptype;
     end;
const maxn=+;
      inf=maxlongint div ;
var head:array[..maxn] of ptype;
    visit:array[..maxn] of boolean;
    d,q:array[..maxn] of longint;
    n,m,i,j,sta,tar,v,a,b,c,cn:longint;
procedure insert(st,ed,r:longint);
var p,q,pre:ptype;
begin
  new(p);
  p^.v:=ed;p^.w:=r;p^.flow:=;p^.next:=nil;
  q:=head[st];
  if q=nil then head[st]:=p
  else
    begin
      while q^.next<>nil do q:=q^.next;
      q^.next:=p;
    end;
end;

function min(a,b:longint):longint;
begin
  if a<b then exit(a) else exit(b);
end;

function bfs:boolean;
var star,rear,x:longint;
    y:ptype;
begin
  fillchar(visit,sizeof(visit),false);
  fillchar(q,sizeof(q),);
  fillchar(d,sizeof(d),);
  star:=;rear:=;q[star]:=sta;d[star]:=;visit[sta]:=true;
  while star<=rear do
    begin
      x:=q[star];
      y:=head[x];
      while y<>nil do
        begin
          if (not visit[y^.v]) and (y^.w>y^.flow) then
            begin
              inc(rear);
              q[rear]:=y^.v;
              visit[y^.v]:=true;
              d[y^.v]:=d[x]+;
            end;
          y:=y^.next;
        end;
      inc(star);
    end;
  bfs:=visit[tar];
end;

procedure decflow(st,ed,delta:longint);
var y:ptype;
begin
  y:=head[st];
  while y^.v<>ed do y:=y^.next;
  dec(y^.flow,delta);
end;

function addflow(p,maxflow:longint):longint;
var y:ptype;
    o:longint;
begin
  if (p=tar) or (maxflow=) then exit(maxflow);
  addflow:=;
  y:=head[p];
  while y<>nil do
    begin
      if (d[y^.v]=d[p]+) and (y^.w>y^.flow) then
        begin
          o:=addflow(y^.v,min(maxflow,y^.w-y^.flow));
          if o> then
            begin
              inc(y^.flow,o);
              decflow(y^.v,p,o);
              inc(addflow,o);
              dec(maxflow,o);
              if maxflow= then break;
            end;
        end;
      y:=y^.next;
    end;
end;

function network:longint;
begin
  network:=;
  while bfs do
    inc(network,addflow(sta,inf));
end;

begin
  assign(input,'profit9.in');reset(input);
  assign(output,'profit9.out');rewrite(output);
  readln(n,m);
  sta:=;tar:=m+n+;
  for i:= to n do
    begin
      read(v);
      insert(m+i,tar,v);
      insert(tar,m+i,);
    end;
  readln;
  for i:= to m do
    begin
      readln(a,b,c);
      insert(i,m+a,inf);insert(m+a,i,);
      insert(i,m+b,inf);insert(m+b,i,);
      insert(sta,i,c);insert(i,sta,);
      cn:=cn+c;
    end;
  writeln(cn-network);
  close(input);close(output);
end.

profit

后来写了个优化是我之前自己发明的decflow，现在我在每条边加了一个域op，指向反向边。速度没有什么提升=w=

program profit2;
type ptype=^node;
     node=record
            v,w,flow:longint;
            next,op:ptype;
     end;
const maxn=+;
      inf=maxlongint div ;
var head:array[..maxn] of ptype;
    visit:array[..maxn] of boolean;
    d,q:array[..maxn] of longint;
    n,m,i,j,sta,tar,v,a,b,c,cn:longint;
procedure insert(st,ed,r1,r2:longint);
var p,q,pre,loc1,loc2:ptype;
begin
  new(p);
  p^.v:=ed;p^.w:=r1;p^.flow:=;p^.next:=nil;
  q:=head[st];
  if q=nil then head[st]:=p
  else
    begin
      while q^.next<>nil do q:=q^.next;
      q^.next:=p;
    end;
  loc1:=p;
  new(p);
  p^.v:=st;p^.w:=r2;p^.flow:=;p^.next:=nil;
  q:=head[ed];
  if q=nil then head[ed]:=p
  else
    begin
      while q^.next<>nil do q:=q^.next;
      q^.next:=p;
    end;
  loc2:=p;
  loc1^.op:=loc2;
  loc2^.op:=loc1;
end;

function min(a,b:longint):longint;
begin
  if a<b then exit(a) else exit(b);
end;

function bfs:boolean;
var star,rear,x:longint;
    y:ptype;
begin
  fillchar(visit,sizeof(visit),false);
  fillchar(q,sizeof(q),);
  fillchar(d,sizeof(d),);
  star:=;rear:=;q[star]:=sta;d[star]:=;visit[sta]:=true;
  while star<=rear do
    begin
      x:=q[star];
      y:=head[x];
      while y<>nil do
        begin
          if (not visit[y^.v]) and (y^.w>y^.flow) then
            begin
              inc(rear);
              q[rear]:=y^.v;
              visit[y^.v]:=true;
              d[y^.v]:=d[x]+;
            end;
          y:=y^.next;
        end;
      inc(star);
    end;
  bfs:=visit[tar];
end;

function addflow(p,maxflow:longint):longint;
var y:ptype;
    o:longint;
begin
  if (p=tar) or (maxflow=) then exit(maxflow);
  addflow:=;
  y:=head[p];
  while y<>nil do
    begin
      if (d[y^.v]=d[p]+) and (y^.w>y^.flow) then
        begin
          o:=addflow(y^.v,min(maxflow,y^.w-y^.flow));
          if o> then
            begin
              inc(y^.flow,o);
              dec(y^.op^.flow,o);
              inc(addflow,o);
              dec(maxflow,o);
              if maxflow= then break;
            end;
        end;
      y:=y^.next;
    end;
end;

function network:longint;
begin
  network:=;
  while bfs do
    inc(network,addflow(sta,inf));
end;

begin
  assign(input,'profit10.in');reset(input);
  assign(output,'profit10.out');rewrite(output);
  readln(n,m);
  sta:=;tar:=m+n+;
  for i:= to n do
    begin
      read(v);
      insert(m+i,tar,v,);
      //insert(tar,m+i,);
    end;
  readln;
  for i:= to m do
    begin
      readln(a,b,c);
      insert(i,m+a,inf,);//insert(m+a,i,);
      insert(i,m+b,inf,);//insert(m+b,i,);
      insert(sta,i,c,);//insert(i,sta,);
      cn:=cn+c;
    end;
  writeln(cn-network);
  close(input);close(output);
end.

profit2