day59（1.18）——leetcode面试经典150

200. 岛屿数量

200. 岛屿数量

题目：

题解：

class Solution {
    int l,r;
    boolean[][] flag;
    int sum = 0; 
    public int numIslands(char[][] grid) {
        l = grid.length;
        r = grid[0].length;
        flag = new boolean[l][r];
        for(int i=0;i<l;i++) {
            for(int j=0;j<r;j++) {
                if(grid[i][j] == '1' && !flag[i][j]) {
                    dfs(grid,i,j);
                    sum++;
                }
            }
        }
        return sum;
    }
    
    public void dfs(char[][] grid, int x, int y) {
        if(x<0 || y<0 || x >= l || y >= r || grid[x][y] == '0' || flag[x][y] == true) {
            return;
        }
        flag[x][y] = true;
        dfs(grid,x+1,y);
        dfs(grid,x,y+1);
        dfs(grid,x-1,y);
        dfs(grid,x,y-1);
    }
}