lightoj 1081 - Square Queries 【二维线段树】

题目链接：lightoj 1081 - Square Queries

题意：给定一个矩阵，每次查询以(x1,y1)为左顶点 、以(x2,y2)为右顶点的子矩阵的最大值。

AC代码：

#include <iostream>#include <cstdio>#include <cstring>#include <cstdlib>#include <cmath>#include <algorithm>#include <vector>#include <queue>#include <map>#include <stack>#define PI acos(-1.0)#define CLR(a, b) memset(a, (b), sizeof(a))#define fi first#define se second#define ll o<<1#define rr o<<1|1using namespace std;typedef long long LL;typedef pair<int, int> pii;const int MAXN = 500 + 10;const int pN = 1e6;// <= 10^7const int INF = 0x3f3f3f3f;const int MOD = 1e9 + 7;void add(LL &x, LL y) { x += y; x %= MOD; }struct Nodey {    int ly, ry;    int Max;};int posx[MAXN], posy[MAXN];int n;struct Nodex {    int lx, rx;    Nodey treey[MAXN<<2];    void Build_y(int o, int l, int r) {        treey[o].ly = l;        treey[o].ry = r;        treey[o].Max = 0;        if(l == r) {            posy[l] = o;            return ;        }        int mid = (l + r) >> 1;        Build_y(ll, l, mid);        Build_y(rr, mid+1, r);    }    int Query_y(int o, int y1, int y2) {        if(treey[o].ly == y1 && treey[o].ry == y2) {            return treey[o].Max;        }        int mid = (treey[o].ly + treey[o].ry) >> 1;        if(y2 <= mid) return Query_y(ll, y1, y2);        else if(y1 > mid) return Query_y(rr, y1, y2);        else return max(Query_y(ll, y1, mid), Query_y(rr, mid+1, y2));    }};Nodex treex[MAXN<<2];void Build_x(int o, int l, int r){    treex[o].lx = l;    treex[o].rx = r;    treex[o].Build_y(1, 1, n);    if(l == r) {        posx[l] = o;        return ;    }    int mid = (l + r) >> 1;    Build_x(ll, l, mid);    Build_x(rr, mid+1, r);}int Query_x(int o, int x1, int x2, int y1, int y2) {    if(treex[o].lx == x1 && treex[o].rx == x2) {        return treex[o].Query_y(1, y1, y2);    }    int mid = (treex[o].lx + treex[o].rx) >> 1;    if(x2 <= mid) return Query_x(ll, x1, x2, y1, y2);    else if(x1 > mid) return Query_x(rr, x1, x2, y1, y2);    else return max(Query_x(ll, x1, mid, y1, y2), Query_x(rr, mid+1, x2, y1, y2));}void PushUp(int nx, int ny, int v) {    treex[nx].treey[ny].Max = max(treex[nx].treey[ny].Max, v);}void Update(int x, int y, int v) {    int sx = posx[x], sy = posy[y];    for(int i = sx; i; i >>= 1) {        for(int j = sy; j; j >>= 1) {            PushUp(i, j, v);        }    }}int main(){    int t, kcase = 1;    scanf("%d", &t);    while(t--)    {        int m; scanf("%d%d", &n, &m);        Build_x(1, 1, n);        for(int i = 1; i <= n; i++) {            for(int j = 1; j <= n; j++) {                int v; scanf("%d", &v);                Update(i, j, v);            }        }        printf("Case %d:\n", kcase++);        while(m--) {            int op, x ,y;            scanf("%d%d%d", &x, &y, &op);            printf("%d\n", Query_x(1, x, x + op - 1, y, y + op - 1));        }    }    return 0;}