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。
1 type 2 tpoint=record 3 l,r,sum,delta,mid:longint; 4 end; 5 var n,m,s,e,i,j,c,sum:longint; 6 tree:array[0..300000] of tpoint; 7 procedure build(x,l,r:longint); 8 begin 9 tree[x].l:=l; tree[x].r:=r; tree[x].sum:=0; tree[x].delta:=0; tree[x].mid:=(l+r) shr 1; 10 if l>=r then exit; 11 build(x*2,l,(l+r) shr 1); 12 build(x*2+1,((l+r) shr 1)+1,r); 13 end; 14 procedure maitain(x:longint); 15 begin 16 tree[x].sum:=0; 17 if tree[x].l<tree[x].r then 18 tree[x].sum:=tree[x*2].sum+tree[x*2+1].sum; 19 tree[x].sum:=abs(tree[x].delta*(tree[x].r-tree[x].l+1)-tree[x].sum); 20 end; 21 procedure insert(x:longint); 22 begin 23 if (s<=tree[x].l) and (tree[x].r<=e) then tree[x].delta:=tree[x].delta xor 1 24 else begin 25 if s<=tree[x].mid then insert(x*2); 26 if e>tree[x].mid then insert(x*2+1); 27 end; 28 maitain(x); 29 end; 30 procedure query(x,add:longint); 31 begin 32 if (s<=tree[x].l) and (tree[x].r<=e) then 33 sum:=sum+abs(add*(tree[x].r-tree[x].l+1)-tree[x].sum) 34 else begin 35 if s<=tree[x].mid then query(x*2,add xor tree[x].delta); 36 if e>tree[x].mid then query(x*2+1,add xor tree[x].delta); 37 end; 38 end; 39 begin 40 readln(n,m); 41 build(1,1,n); 42 for i:=1 to m do 43 begin 44 readln(c,s,e); 45 sum:=0; 46 if c=0 then insert(1) 47 else begin 48 query(1,0); 49 writeln(sum); 50 end; 51 end; 52 end.
(转载请注明出处：http://www.cnblogs.com/Kalenda/)
