LeetCode 200.岛屿数量(JAVA)

class Solution {
    public int numIslands(char[][] grid) {
    	// DFS
        // 判断特例
        if (grid.length == 0 || grid[0].length == 0)
            return 0;
        int cnt = 0;
        // 遍历
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j] == '1') {
                    cnt++;
                    dfs(grid, i, j);
                }
            }
        }
        return cnt;
    }

    private void dfs(char[][] grid, int i, int j) {
        // 判断特例,
        if (i < 0 || j < 0 || i >= grid.length || j >= grid[i].length || grid[i][j] != '1')
            return;
        grid[i][j] = '0';
        dfs(grid, i - 1, j);
        dfs(grid, i + 1, j);
        dfs(grid, i, j - 1);
        dfs(grid, i, j + 1);
    }
}