class Solution {
    private int[] p;

    public int largestArea(String[] grid) {
        int m = grid.length;
        int n = grid[0].length();
        p = new int[m * n + 1];
        int[] size = new int[m * n + 1];
        for (int i = 0; i < p.length; ++i) {
            p[i] = i;
            size[i] = 1;
        }
        int[] dirs = {0, 1, 0, -1, 0};
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (i == 0 || i == m - 1 || j == 0 || j == n - 1 || grid[i].charAt(j) == '0') {
                    p[find(i * n + j)] = find(m * n);
                } else {
                    for (int k = 0; k < 4; ++k) {
                        int x = i + dirs[k];
                        int y = j + dirs[k + 1];
                        if (grid[x].charAt(y) == '0' || grid[i].charAt(j) == grid[x].charAt(y)) {
                            if (find(x * n + y) != find(i * n + j)) {
                                size[find(x * n + y)] += size[find(i * n + j)];
                                p[find(i * n + j)] = find(x * n + y);
                            }
                        }
                    }
                }
            }
        }
        int ans = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (find(i * n + j) != find(m * n)) {
                    ans = Math.max(ans, size[i * n + j]);
                }
            }
        }
        return ans;
    }

    private int find(int x) {
        if (p[x] != x) {
            p[x] = find(p[x]);
        }
        return p[x];
    }
}