HDU 1559 二维树状数组

传送门：HDU 1559

模板题， 注意矩阵sum树状数组求和

AC code:

/*adrui's submission *Language : C++ *Result : Accepted *File Name: HDU 3333 *Favorite : Dragon Balls *love : yy *Standing in the Hall of Fame */#include<iostream>#include<cstring>#include<map>#include<algorithm>using namespace std;typedef long long LL;#define debug 0#define inf 0x3f3f3f3f#define M(a, b) memset(a, b, sizeof(a))#define lowbit(x) (x & (-x))const int maxn = 1000 + 5;int m, n, x, y;LL c[maxn][maxn];void add(int x, int y, LL v) {    for (int i = x; i <= m; i += lowbit(i))        for (int j = y; j <= n; j += lowbit(j)) {            c[i][j] += v;        }}LL getSum(int x, int y) {    LL res = 0;    for (int i = x; i; i -= lowbit(i))        for (int j = y; j; j -= lowbit(j)) {            res += c[i][j];        }    return res;}int main() {#if debug    freopen("in.txt", "r", stdin);#endif //debug    cin.tie(0);    cin.sync_with_stdio(false);    int t;    LL a;    cin >> t;    while (t--) {        M(c, 0);        cin >> m >> n >> x >> y;        for (int i = 1; i <= m; ++i)            for (int j = 1; j <= n; ++j) {                cin >> a;                add(i, j, a);            }        LL mx = -inf;        for (int i = x; i <= m; ++i)            for (int j = y; j <= n; ++j) {                LL tmp = getSum(i, j) - getSum(i - x, j) - getSum(i, j - y) + getSum(i - x, j - y);                mx = max(mx, tmp);            }        cout << mx << endl;    }    return 0;}