POJ 1195 二維樹狀數組

題意：給定一個座標系，每個點有一個值，值可以改變，求任意矩形所圍的值得大小。

#include <iostream>using namespace std;#define S 1025int c[S][S], n;int lowbit ( int x ){return x & ( -x );}void modify ( int x, int y, int v ){int i, j;for ( i = x; i <= n; i += lowbit(i) ){for ( j = y; j <= n; j += lowbit(j) )c[i][j] += v;}}int sum ( int x, int y ){int i, j, sum = 0;for ( i = x; i > 0; i -= lowbit(i) ){for ( j = y; j > 0; j -= lowbit(j) )sum += c[i][j];}return sum;}int getSum ( int x1, int y1, int x2, int y2 ){return sum(x2,y2) - sum(x2,y1-1) - sum(x1-1,y2) + sum(x1-1,y1-1);}int main(){int oper, x1, y1, x2, y2, v;scanf("%d%d",&oper,&n);memset(c,0,sizeof(c));while ( scanf("%d",&oper) && oper != 3 ){if ( oper == 1 ){scanf("%d%d%d",&x1,&y1,&v);modify ( x1+1, y1+1, v );}else if ( oper == 2 ){scanf("%d%d%d%d",&x1,&y1,&x2,&y2);printf("%d\n", getSum ( x1+1, y1+1, x2+1, y2+1 ) );}}return 0;}