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。

 1 type
 2   node=record
 3     f,t:longint;
 4   end;
 5 var p,c,n,i,j,f,t,sum:longint;
 6 head:array[0..30001] of longint;
 7 can:array[0..30001] of boolean;
 8 b:array[0..200001] of node;
 9 q:array[0..6000000] of longint;
10 procedure insert(m,f,t:longint);
11 begin
12   b[m].f:=head[f];
13   b[m].t:=t;
14   head[f]:=m;
15 end;
16 procedure delete(j:longint);
17 var nowe:longint;
18 begin
19   nowe:=head[j];
20   while nowe<>0 do
21     begin
22       can[b[nowe].t]:=false;
23       nowe:=b[nowe].f;
24     end;
25 end;
26 procedure bfs;
27 var l,r,now,nowe:longint;
28 begin
29   l:=1; r:=1; q[1]:=1; can[1]:=false;
30   while l<=r do
31     begin
32       now:=q[l];
33       nowe:=head[now];
34       while nowe<>0 do
35         begin
36           if can[b[nowe].t] then begin
37             //writeln(b[nowe].t);
38             can[b[nowe].t]:=false;
39             inc(r);
40             //inc(sum);
41             q[r]:=b[nowe].t;
42           end;
43           nowe:=b[nowe].f;
44         end;
45       inc(l);
46     end;
47   sum:=r;
48 end;
49 begin
50   readln(p,c,n);
51   fillchar(can,sizeof(can),true);
52   for i:=1 to c do
53     begin
54       readln(f,t);
55       if f=t then continue;
56       insert(2*i-1,f,t);
57       insert(2*i,t,f);
58     end;
59   for i:=1 to n do
60     begin
61       readln(j);
62       can[j]:=false;
63       delete(j);
64     end;
65   bfs;
66   writeln(p-sum);
67 end.

type
  node=record
    f,t:longint;
  end;
var p,c,n,i,j,f,t,sum:longint;
head:array[0..30001] of longint;
can:array[0..30001] of boolean;
b:array[0..200001] of node;
q:array[0..6000000] 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<>0 do
    begin
      can[b[nowe].t]:=false;
      nowe:=b[nowe].f;
    end;
end;
procedure bfs;
var l,r,now,nowe:longint;
begin
  l:=1; r:=1; q[1]:=1; can[1]:=false;//sum:=1;
  while l<=r do
    begin
      now:=q[l];
      nowe:=head[now];
      while nowe<>0 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:=1 to c do
    begin
      readln(f,t);
      if f=t then continue;
      insert(2*i-1,f,t);
      insert(2*i,t,f);
    end;
  for i:=1 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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