【DFS】695.岛屿的最大面积

题目

法1：DFS

最简单的DFS必须掌握！！！

class Solution {
    public int maxAreaOfIsland(int[][] grid) {
        int m = grid.length, n = grid[0].length, ans = 0;
        if (m == 0 || n == 0) {
            return ans;
        }
        boolean[][] visited = new boolean[m][n];
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == 1 && !visited[i][j]) {
                    ans = Math.max(ans, dfs(grid, visited, i, j));
                }
            }
        }

        return ans;
    }

    public int dfs(int[][] grid, boolean[][] visited, int i, int j) {
        if (i >= 0 && i < grid.length 
                && j >= 0 && j < grid[0].length 
                && grid[i][j] == 1 
                && !visited[i][j]) {
            visited[i][j] = true;
            return 1 + dfs(grid, visited, i - 1, j) 
                    + dfs(grid, visited, i + 1, j)
                    + dfs(grid, visited, i, j - 1)
                    + dfs(grid, visited, i, j + 1);  
        }
        return 0;
    }
}