200.岛屿数量.java

/*
 * @lc app=leetcode.cn id=200 lang=java
 *
 * [200] 岛屿数量
 */

// @lc code=start
class Solution {
    public int numIslands(char[][] grid) {
        int count = 0;
        for(int i =0; i < grid.length;i++){
            for(int j = 0; j < grid[i].length;j++){
                if(grid[i][j] == '1'){
                    dfs(grid, i, j);
                    count++;
                }
            }
        }
        return count;
    }

    private void dfs(char[][] grid, int i, int j){
        int n = grid.length;
        int m = grid[n].length;
        if(i < 0 || j<0 || i >=n||j>=m){
            return;
        }
        if(grid[i][j] == '0' || grid[i][j] == '2'){
            return;
        }
        grid[i][j] = '2';
        dfs(grid, i, j-1);
        dfs(grid, i, j+1);
        dfs(grid, i-1, j);
        dfs(grid, i+1, j);
    }
}
// @lc code=end