Solution695.java

package array_problem;

public class Solution695 {

    private int m, n;
    private int[][] d = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

    public int maxAreaOfIsland(int[][] grid) {

        if (grid == null || grid.length == 0) {
            return 0;
        }
        m = grid.length;
        n = grid[0].length;

        int maxArea = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                maxArea = Math.max(maxArea, dfs(grid, i, j));
            }
        }

        return maxArea;
    }

    private int dfs(int[][] grid, int i, int j) {

        if (i < 0 || i >= m || j < 0 || j >= m || grid[i][j] == 0) {
            return 0;
        }

        // 已经搜索过的设为0，防止重复被搜索
        grid[i][j] = 0;
        int res = 1;
        for (int[] d : d) {
            res += dfs(grid, i + d[0], j + d[1]);
        }
        return res;
    }

}