dfs島嶼數量（LeetCode200. 島嶼數量）

package dfs;
//主要是遞歸的思路
public class Land {
    //leetcode 200. 島嶼數量
    public int numIslands(char[][] grid) {
        int sum = 0;
        if (grid == null || grid.length == 0) {
            return sum;
        }
        int x = grid.length;
        int y = grid[0].length;
        for (int i = 0; i < x; i++) {
            for (int j = 0; j < y; j++) {
                if (grid[i][j] == '1') {
                    sum++;
                    dfs(grid, i, j);
                }
            }
        }
        return sum;
    }

    public void dfs (char[][] grid, int x, int y){
        if (x < 0 || x >= grid.length || y < 0 || y >= grid[0].length || grid[x][y] == '0') {
            return;
        }
        grid[x][y] = '0';
        dfs(grid, x + 1, y);
        dfs(grid, x - 1, y);
        dfs(grid, x, y + 1);
        dfs(grid, x, y - 1);
    }

    public static void main(String[] args) {
        char[][] chars = {
                {'1','1','0','1','0'},
                {'1','1','0','1','0'},
                {'1','1','0','0','1'},
                {'0','0','1','0','1'}
        };
        Land land = new Land();
        System.out.println(land.numIslands(chars));
    }
}