最大子矩阵 蓝桥杯 暴力枚举 剪枝

⭐ 最大子矩阵

3 4
2 0 7 9
0 6 9 7
8 4 6 4
8

样例输出

6	

---

package algorithm.lanQiao.暴力剪枝;

import java.io.*;

public class 最大子矩阵
{
	static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
	static BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));

	public static void main(String[] args) throws IOException
	{
		String[] ss = in.readLine().split(" ");
		int n = Integer.parseInt(ss[0]);
		int m = Integer.parseInt(ss[1]);

		int[][] g = new int[n][m];
		for (int i = 0; i < n; i++)
		{
			ss = in.readLine().split(" ");
			for (int j = 0; j < m; j++)
				g[i][j] = Integer.parseInt(ss[j]);
		}
		int limit = Integer.parseInt(in.readLine());
		int res = 1;

		for (int i = 0; i < n; i++)// 枚举 行首
			for (int j = 0; j < m; j++)// 枚举 列首
				for (int x = i; x < n; x++)// 枚举 行尾
				{
				//	投机取巧小剪枝（过最后的 10% 案例）
					int kx = Integer.MAX_VALUE;
					int ky = Integer.MAX_VALUE;

					for (int y = j; y < m; y++)// 枚举 列尾
					{
						if (x >= kx && y >= ky)
							continue;

						if (check(g, i, j, x, y) <= limit)// 判断最大差
						{
							res = Math.max(res, (x - i + 1) * (y - j + 1));
						} else
						{
							kx = x;
							ky = y;
							break;
						}
					}
				}

		System.out.println(res);
	}

	private static int check(int[][] g, int xs, int ys, int xe, int ye)
	{
		int max = Integer.MIN_VALUE;
		int min = Integer.MAX_VALUE;

		for (int i = xs; i <= xe; i++)
			for (int j = ys; j <= ye; j++)
			{
				max = Math.max(max, g[i][j]);
				min = Math.min(min, g[i][j]);
			}

		return max - min;
	}

}