hdu2642Stars

二维树状数组，单点更新区间查询，标记一下黑暗的星星亮，亮的星星黑暗，就变成了+1-1的操作了。再就是注意x1,y1,x2,y2不能0，得先++。

#include<cstdio>#include<string>#include<cstring>#include<iostream>#include<algorithm>#define LL long longconst int maxn =  1010;using namespace std;int b[maxn][maxn],n,T,book[maxn][maxn],x1,x2,y1,y2,n1,bj[maxn][maxn];int lowbit(int x){    return x&(-x);}void add(int x,int y,int dd){    for(int i=x; i< maxn; i+=lowbit(i))    {        for(int j=y; j< maxn; j+=lowbit(j))        {            b[i][j]+=dd;        }    }}int sum(int i,int j){    int sum=0;    for(int x=i; x>0; x-=lowbit(x))    {        for(int y=j; y>0; y-=lowbit(y))        {            sum+=b[x][y];        }    }    return sum;}int main(){    scanf("%d",&T);    memset(b,0,sizeof(b));    memset(bj,0,sizeof(bj));    while(T--)    {        getchar();        char a;        scanf("%c",&a);        if(a=='B')        {            scanf("%d %d",&x1,&y1);            x1++,y1++;            if(bj[x1][y1]==0)                add(x1,y1,1),bj[x1][y1]=1;        }        else if(a=='D')        {            scanf("%d %d",&x1,&y1);            x1++,y1++;            if(bj[x1][y1]==1)                add(x1,y1,-1),bj[x1][y1]=0;        }        else if(a=='Q')        {            scanf("%d %d %d %d",&x1,&x2,&y1,&y2);            x1++,y1++,x2++,y2++;            if(x1>x2)swap(x1,x2);            if(y1>y2)swap(y1,y2);            printf("%d\n",sum(x2,y2)+sum(x1-1,y1-1)-sum(x2,y1-1)-sum(x1-1,y2));        }    }    return 0;}