POJ2155 Matrix

  題目鏈接：http://poj.org/problem?id=2155

  二維樹狀數組+容斥，注意要向上統計，向下修改

  注意c[i][j]的意義是A[i][j]修改後的值

  貼代碼

#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstring>
using namespace std;
int const maxn=1005;
int c[maxn][maxn];
int Q,n;
int lowbit(int x){
	return x&-x;
}
void add(int x,int y){
	for(int i=x;i<=n;i+=lowbit(i))
		for (int j=y;j<=n;j+=lowbit(j)) c[i][j]=(c[i][j]+1)%2;
}
int query(int x,int y){
	int sum=0;
	for (int i=x;i>=1;i-=lowbit(i))
		  for (int j=y;j>=1;j-=lowbit(j))sum=(sum+c[i][j])%2;
    return sum;
}
int main(){
	freopen("2155.in","r",stdin);
	freopen("2155.out","w",stdout);
	scanf("%d\n",&Q);
	if (Q==0)printf("\n");
	while(Q--){
		int Q1; 
		scanf("%d%d\n",&n,&Q1);
		memset(c,0,sizeof(c));
		while(Q1--){
			char ch;
			scanf("%c",&ch);
			if (ch=='C'){
				int x1,y1,x2,y2;
				scanf("%d%d%d%d\n",&x1,&y1,&x2,&y2);
				add(x1,y1);add(x1,y2+1);add(x2+1,y1);add(x2+1,y2+1);
			}else {
				int x,y;
				scanf("%d%d\n",&x,&y);
				printf("%d\n",query(x,y));
			}
		}
		if (Q) printf("\n");
	}
	return 0;
} 

【寫的有漏洞的，歡迎路過大神吐槽】

  2017/07/06 16:56:20

  Ending.