HDU 2888 Check Corners

本文介绍了一种高效解决矩阵中子区域最大值查询的方法,通过预处理建立二维稀疏表,实现快速查询子矩阵的最大值,并判断该最大值是否位于子矩阵的四个角上。

Check Corners

Time Limit: 2000/10000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 2835    Accepted Submission(s): 1005

Problem Description
Paul draw a big m*n matrix A last month, whose entries Ai,j are all integer numbers ( 1 <= i <= m, 1 <= j <= n ). Now he selects some sub-matrices, hoping to find the maximum number. Then he finds that there may be more than one maximum number, he also wants to know the number of them. But soon he find that it is too complex, so he changes his mind, he just want to know whether there is a maximum at the four corners of the sub-matrix, he calls this “Check corners”. It’s a boring job when selecting too many sub-matrices, so he asks you for help. (For the “Check corners” part: If the sub-matrix has only one row or column just check the two endpoints. If the sub-matrix has only one entry just output “yes”.)
 
Input
There are multiple test cases.
For each test case, the first line contains two integers m, n (1 <= m, n <= 300), which is the size of the row and column of the matrix, respectively. The next m lines with n integers each gives the elements of the matrix which fit in non-negative 32-bit integer.
The next line contains a single integer Q (1 <= Q <= 1,000,000), the number of queries. The next Q lines give one query on each line, with four integers r1, c1, r2, c2 (1 <= r1 <= r2 <= m, 1 <= c1 <= c2 <= n), which are the indices of the upper-left corner and lower-right corner of the sub-matrix in question.
 
Output
For each test case, print Q lines with two numbers on each line, the required maximum integer and the result of the “Check corners” using “yes” or “no”. Separate the two parts with a single space.
 
Sample Input
4 4
4 4 10 7
2 13 9 11
5 7 8 20
13 20 8 2
4
1 1 4 4
1 1 3 3
1 3 3 4
1 1 1 1
 
Sample Output
20 no
13 no
20 yes
4 yes
 
 1 #include <iostream>
 2 #include <cmath>
 3 using namespace std;
 4 int dp[302][302][9][9];
 5 int num[302][302];
 6 int n,m;
 7 void init_RMQ(){
 8     for(int i=1;i<=n;i++){
 9         for(int j=1;j<=m;j++){
10             dp[i][j][0][0]=num[i][j];
11         }
12     }
13     int kr = (int)(log((double)(n))/log(2.0));
14     int kc = (int)(log((double)(m))/log(2.0));
15     for(int i=0;i<=kr;i++){
16         for(int j=0;j<=kc;j++){
17             if(i==0&&j==0){
18                 continue;
19             }
20             for(int r=1;r+(1<<i)-1<=n;r++){
21                 for(int c=1;c+(1<<j)-1<=m;c++){
22                     if(i==0){
23                         dp[r][c][i][j]=max(dp[r][c][i][j-1],dp[r][c+(1<<(j-1))][i][j-1]);//左右合并,取y/2为分割线
24                     }
25                     else{
26                         dp[r][c][i][j]=max(dp[r][c][i-1][j],dp[r+(1<<(i-1))][c][i-1][j]);//上下合并,取x/2为分割线
27                     }
28                 }
29             }
30         }
31     }
32 }
33 
34 int RMQ(int r1,int c1,int r2,int c2){
35     int kr = (int)(log((double)(r2-r1+1))/log(2.0));
36     int kc = (int)(log((double)(c2-c1+1))/log(2.0));
37     return max(max(dp[r1][c1][kr][kc],dp[r2-(1<<kr)+1][c1][kr][kc]),max(dp[r1][c2-(1<<kc)+1][kr][kc],dp[r2-(1<<kr)+1][c2-(1<<kc)+1][kr][kc]));
38 }
39 
40 int main(){
41     cin.sync_with_stdio(false);
42     while(cin>>n>>m){
43         for(int i=1;i<=n;i++){
44             for(int j=1;j<=m;j++){
45                 cin>>num[i][j];
46             }
47         }
48         init_RMQ();
49         int t,a,b,c,d;
50         cin>>t;
51         while(t--){
52             cin>>a>>b>>c>>d;
53             int ans = RMQ(a,b,c,d);
54             cout<<ans<<" ";
55             if(ans==num[a][b]||ans==num[a][d]||ans==num[c][b]||ans==num[c][d]){
56                 cout<<"yes"<<endl;
57             }
58             else{
59                 cout<<"no"<<endl;
60             }
61         }
62     }
63     return 0;
64 }

2017-01-24 11:11:11

 

转载于:https://www.cnblogs.com/xjh-shin/articles/6346700.html

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