二维线段树题，求矩阵内的子矩阵中最小的值

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 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 #define lson l,m,rt<<1
 5 #define rson m+1,r,rt<<1|1
 6 #define maxn 301
 7 int a[maxn][maxn];
 8 int setree[maxn<<2][maxn<<2];
 9 int n;
10 void build1(int num1,int num2,int l,int r,int rt)
11 {
12     if(l==r){
13         setree[rt][num1]=a[l][num2];
14         return;
15     }
16     int m=(l+r)>>1;
17     build1(num1,num2,lson);
18     build1(num1,num2,rson);
19     setree[rt][num1]=min(setree[rt<<1][num1],setree[rt<<1|1][num1]);
20 }
21 void build2(int num,int l,int r,int rt)
22 {
23     setree[rt][num]=min(setree[rt][num<<1],setree[rt][num<<1|1]);
24     if(l==r)
25     return;
26     int m=(l+r)>>1;
27     build2(num,lson);
28     build2(num,rson);
29 }
30 void build(int l,int r,int rt)
31 {
32     if(l==r){
33         build1(rt,l,1,n,1);
34         return;
35     }
36     int m=(l+r)>>1;
37     build(lson);
38     build(rson);
39     build2(rt,1,n,1);
40 }
41 int subquery(int num,int l,int r,int rt,int L,int R)
42 {
43     if(L<=l&&r<=R)
44     return setree[rt][num];
45     int m=(l+r)>>1;
46     int ans=1<<31-1;
47     if(L<=m)
48     ans=min(ans,subquery(num,lson,L,R));
49     if(R>m)
50     ans=min(ans,subquery(num,rson,L,R));
51     return ans;
52 }
53 int query(int l,int r,int rt,int L,int R,int l1,int r1)
54 {
55     if(L<=l&&r<=R)
56     return subquery(rt,1,n,1,l1,r1);
57     int m=(l+r)>>1;
58     int ans=1<<31-1;
59     if(L<=m)
60     ans=min(ans,query(lson,L,R,l1,r1));
61     if(R>m)
62     ans=min(ans,query(rson,L,R,l1,r1));
63     return ans;
64 }
65 int main()
66 {
67     int t;
68     scanf("%d",&t);
69     while(t--){
70         scanf("%d",&n);
71         for(int i=1;i<=n;i++)
72         for(int j=1;j<=n;j++)
73         scanf("%d",&a[i][j]);
74         build(1,n,1);
75         int m;
76         scanf("%d",&m);
77         while(m--){
78             int a,b,c,d;
79             scanf("%d%d%d%d",&a,&b,&c,&d);
80             printf("%d\n",query(1,n,1,b,d,a,c));
81         }
82     }
83     return 0;
84 }