题解 | #求最大子矩阵的大小#

import java.util.Stack;
import java.util.Scanner;

public class Main { 
    public static int maxRecSize(int[][] map) {
        if (map == null || map.length == 0 || map[0].length == 0)
            return 0;
        int maxArea = 0;
        int[] height = new int [map[0].length];
        for (int i = 0; i < map.length; i++) {
            for (int j = 0; j < map[0].length; j++)
                height[j] = map[i][j] == 0 ? 0 : height[j] + 1;
            maxArea = Math.max(maxRecFromBottom(height), maxArea);
        }
        return maxArea;
    }
    
    public static int maxRecFromBottom(int[] height) {
        if (height == null || height.length == 0)
            return 0;
        int maxArea = 0;
        Stack<Integer> stack = new Stack<Integer>();
        for (int i = 0; i < height.length; i++) {
            while (!stack.isEmpty() && height[i] <= height[stack.peek()]) {
                int j = stack.pop();
                int k = stack.isEmpty() ? -1 : stack.peek();
                int curArea = (i - k - 1) * height[j];
                maxArea = Math.max(maxArea, curArea);
            }
            stack.push(i);
        }
        while (!stack.isEmpty()) {
            int j = stack.pop();
            int k = stack.isEmpty() ? -1 : stack.peek();
            int curArea = (height.length - k - 1) * height[j];
            maxArea = Math.max(maxArea, curArea);
        }
        return maxArea;
    }
    
    public static void main(String[] args) {
        //int n, m;
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextInt()) {
            int n = sc.nextInt();
            int m = sc.nextInt();
            int[][] map = new int[n][m];
            for (int i = 0; i < n; ++i) 
                for (int j = 0; j < m; ++j) 
                    map[i][j] = sc.nextInt();
            System.out.println(maxRecSize(map));
        } 
    }
}