P1230: [Usaco2008 Nov]lites 开关灯

嗯嗯，这是一道线段树的题，询问区间内亮着的灯的个数，我们可以把区间修改的线段树改一下，原本的求和改成若有奇数次更改则取反（总长度-亮着的灯个数），而判断是否奇数次只要数组加一个delta的值，update的时候delta xor 1 就够了，代码如下。

 type
   tpoint=record
     l,r,sum,delta,mid:longint;
   end;
 var n,m,s,e,i,j,c,sum:longint;
 tree:array[..] of tpoint;
 procedure build(x,l,r:longint);
 begin
   tree[x].l:=l; tree[x].r:=r; tree[x].sum:=; tree[x].delta:=; tree[x].mid:=(l+r) shr ;
   if l>=r then exit;
   build(x*,l,(l+r) shr );
   build(x*+,((l+r) shr )+,r);
 end;
 procedure maitain(x:longint);
 begin
   tree[x].sum:=;
   if tree[x].l<tree[x].r then
     tree[x].sum:=tree[x*].sum+tree[x*+].sum;
   tree[x].sum:=abs(tree[x].delta*(tree[x].r-tree[x].l+)-tree[x].sum);
 end;
 procedure insert(x:longint);
 begin
   if (s<=tree[x].l) and (tree[x].r<=e) then tree[x].delta:=tree[x].delta xor
     else begin
       if s<=tree[x].mid then insert(x*);
       if e>tree[x].mid then insert(x*+);
     end;
   maitain(x);
 end;
 procedure query(x,add:longint);
 begin
   if (s<=tree[x].l) and (tree[x].r<=e) then
     sum:=sum+abs(add*(tree[x].r-tree[x].l+)-tree[x].sum)
   else begin
     if s<=tree[x].mid then query(x*,add xor tree[x].delta);
     if e>tree[x].mid then query(x*+,add xor tree[x].delta);
   end;
 end;
 begin
   readln(n,m);
   build(,,n);
   for i:= to m do
     begin
       readln(c,s,e);
       sum:=;
       if c= then insert()
         else begin
           query(,);
           writeln(sum);
         end;
     end;
 end.

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