P1574: [Usaco2009 Jan]地震损坏Damage

卧槽卧槽卧槽，这道水题竟然让我WA了两遍！！评测系统卡了然后手贱又提交了一次，然后就悲催了呜呜。。

把与不能回家但牛棚完好的牛相邻的牛棚赋值为不能走(false)，可以证明，如果该牛回不了家，则周围一圈的牛要么牛棚坏了，要么也是一样回不了，所以结果就是，该牛周围的牛都回不了牛庄，所以是一道贪心题，最后来一遍bfs搜索有多少牛可以回去，总数一减就是答案了。

 type
   node=record
     f,t:longint;
   end;
 var p,c,n,i,j,f,t,sum:longint;
 head:array[..] of longint;
 can:array[..] of boolean;
 b:array[..] of node;
 q:array[..] of longint;
 procedure insert(m,f,t:longint);
 begin
   b[m].f:=head[f];
   b[m].t:=t;
   head[f]:=m;
 end;
 procedure delete(j:longint);
 var nowe:longint;
 begin
   nowe:=head[j];
   while nowe<> do
     begin
       can[b[nowe].t]:=false;
       nowe:=b[nowe].f;
     end;
 end;
 procedure bfs;
 var l,r,now,nowe:longint;
 begin
   l:=; r:=; q[]:=; can[]:=false;
   while l<=r do
     begin
       now:=q[l];
       nowe:=head[now];
       while nowe<> do
         begin
           if can[b[nowe].t] then begin
             //writeln(b[nowe].t);
             can[b[nowe].t]:=false;
             inc(r);
             //inc(sum);
             q[r]:=b[nowe].t;
           end;
           nowe:=b[nowe].f;
         end;
       inc(l);
     end;
   sum:=r;
 end;
 begin
   readln(p,c,n);
   fillchar(can,sizeof(can),true);
   for i:= to c do
     begin
       readln(f,t);
       if f=t then continue;
       insert(*i-,f,t);
       insert(*i,t,f);
     end;
   for i:= to n do
     begin
       readln(j);
       can[j]:=false;
       delete(j);
     end;
   bfs;
   writeln(p-sum);
 end.

 type
   node=record
     f,t:longint;
   end;
 var p,c,n,i,j,f,t,sum:longint;
 head:array[..] of longint;
 can:array[..] of boolean;
 b:array[..] of node;
 q:array[..] of longint;
 procedure insert(m,f,t:longint);
 begin
   b[m].f:=head[f];
   b[m].t:=t;
   head[f]:=m;
 end;
 procedure delete(j:longint);
 var nowe:longint;
 begin
   nowe:=head[j];
   while nowe<> do
     begin
       can[b[nowe].t]:=false;
       nowe:=b[nowe].f;
     end;
 end;
 procedure bfs;
 var l,r,now,nowe:longint;
 begin
   l:=; r:=; q[]:=; can[]:=false;//sum:=1;
   while l<=r do
     begin
       now:=q[l];
       nowe:=head[now];
       while nowe<> do
         begin
           //if (b[nowe].t=4) and (can[b[nowe].t]) then writeln('sb');
           if can[b[nowe].t] then begin
             //writeln(b[nowe].t);
             can[b[nowe].t]:=false;
             inc(r);
             //inc(sum);
             q[r]:=b[nowe].t;
           end;
           nowe:=b[nowe].f;
         end;
       inc(l);
     end;
   sum:=r;
 end;
 begin
   readln(p,c,n);
   fillchar(can,sizeof(can),true);
   for i:= to c do
     begin
       readln(f,t);
       if f=t then continue;
       insert(*i-,f,t);
       insert(*i,t,f);
     end;
   for i:= to n do
     begin
       readln(j);
       can[j]:=false;
       delete(j);
     end;
   //for i:=1 to p do
     //if can[i] then writeln('t')
       //else writeln('f');
   bfs;
   writeln(p-sum);
 end.

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