POJ 1656 二維樹狀數組

題意：給定100*100的網格，每個格子可以塗上黑色或者白色（初始時全部樹白色），經過一系列操作後輸出任意一個正方形地區內的黑色格子數。

#include <iostream>using namespace std;int c[110][110];int a[110][110];const int n = 100;int lowbit ( int x ){return x & ( -x );}void modify ( int x, int y, int v ){for ( int i = x; i <= n; i += lowbit(i) ){for ( int j = y; j <= n; j += lowbit(j) )c[i][j] += v;}}void update ( int x, int y, int l, int mark ){int x1 = x, x2 = x + l - 1, y1 = y, y2 = y + l - 1;for ( int i = x1; i <= x2; ++i ){for ( int j = y1; j <= y2; ++j ){if ( a[i][j] != mark ){a[i][j] = mark;modify ( i, j, mark );}}}}int sum ( int x, int y ){int total = 0;for ( int i = x; i > 0; i -= lowbit(i) ){for ( int j = y; j > 0; j -= lowbit(j) )total += c[i][j];}return total;}int getSum ( int x, int y, int l ){int x1 = x, y1 = y, x2 = x + l - 1, y2 = y + l - 1;return sum ( x2, y2 ) - sum ( x1-1, y2 ) - sum( x2 , y1 - 1 ) + sum ( x1 - 1, y1 - 1);}int main(){int t, x, y, l;char oper[10];memset(c,0,sizeof(c));memset(a,-1,sizeof(a));scanf("%d", &t );while ( t-- ){scanf("%s", oper );scanf("%d%d%d", &x, &y, &l );if ( strcmp(oper, "BLACK") == 0 )update ( x, y, l, 1 );else if ( strcmp(oper, "WHITE") == 0 )update ( x, y, l, -1 );elseprintf ( "%d\n", getSum ( x, y, l ) );}return 0;}

此題直接求解0MS

#include <iostream>using namespace std;int a[110][110];void update ( int x1, int y1, int x2, int y2, bool mark ){for ( int i = x1; i <= x2; ++i )for ( int j = y1; j <= y2; ++j )a[i][j] = mark;}int getSum ( int x1, int y1, int x2, int y2 ){int i, j, sum = 0;for ( i = x1; i <= x2; ++i )for ( j = y1; j <= y2; ++j )if ( a[i][j] )++sum;return sum;}int main(){int t, x, y, l;char oper[10];memset(a,0,sizeof(a));scanf("%d", &t );while ( t-- ){scanf("%s", oper );scanf("%d%d%d", &x, &y, &l );if ( strcmp(oper, "BLACK") == 0 )update ( x, y, x+l-1, y+l-1, 1 );else if ( strcmp(oper, "WHITE") == 0 )update ( x, y, x+l-1, y+l-1, 0 );elseprintf ( "%d\n", getSum ( x, y, x+l-1, y+l-1 ) );}return 0;}