ARC081-F

F.java

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class F {
    public static void main(String[] args) {
        InputReader in = new InputReader(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int H = in.nextInt();
        int W = in.nextInt();

        int[][] table = new int[H][W];
        for (int i = 0; i < H ; i++) {
            char[] c = in.nextToken().toCharArray();
            for (int j = 0; j < W ; j++) {
                table[i][j] = c[j] == '.' ? 0 : 1;
            }
        }

        int[][] diff = new int[H][W-1];
        for (int i = 0 ; i < H ; i++) {
            for (int j = 0; j+1 < W; j++) {
                diff[i][j] = table[i][j] ^ table[i][j+1];
            }
        }

        W--;
        int[] bottom = new int[W];
        for (int j = 0; j < W ; j++) {
            int shouldSameTo = 0;
            while (bottom[j] < H && diff[bottom[j]][j] == diff[shouldSameTo][j]) {
                bottom[j]++;
            }
        }

        int answer = Math.max(H, W+1);
        int[] height = new int[W];
        for (int i = 0 ; i < H ; i++) {
            for (int j = 0; j < W ; j++) {
                height[j] = bottom[j] - i;
            }
            answer = Math.max(answer, solve(height));

            for (int j = 0; j < W ; j++) {
                if (bottom[j] == i+1) {
                    int shouldSameTo = bottom[j];
                    while (bottom[j] < H && diff[bottom[j]][j] == diff[shouldSameTo][j]) {
                        bottom[j]++;
                    }
                }
            }
        }
        out.println(answer);
        out.flush();
    }

    static int solve(int[] a) {
        int n = a.length;
        int[] stk = new int[n+1];
        int head = 0;

        int[] l = new int[n];
        for (int i = 0 ; i < n ; i++) {
            while (head > 0 && a[stk[head-1]] >= a[i]) {
                head--;
            }
            l[i] = head == 0 ? 0 : stk[head-1]+1;
            stk[head++] = i;
        }

        int[] r = new int[n];
        head = 0;
        for (int i = n-1 ; i >= 0 ; i--) {
            while (head > 0 && a[stk[head-1]] >= a[i]) {
                head--;
            }
            r[i] = head == 0 ? n : stk[head-1];
            stk[head++] = i;
        }

        int max = 0;
        for (int i = 0; i < n ; i++) {
            max = Math.max(max, a[i] * (r[i] - l[i] + 1));
        }
        return max;
    }
}