世界國家島嶼數量排名，島嶼數量

class Solution {// 計算島嶼數量public int numIslands(char[][] grid) {int islandNum = 0;for(int i = 0; i < grid.length; i++){for(int j = 0; j < grid[0].length; j++){if(grid[i][j] == '1'){infect(grid, i, j);islandNum++;}}}return islandNum;}//感染函數public void infect(char[][] grid, int i, int j){if(i < 0 || i >= grid.length ||j < 0 || j >= grid[0].length || grid[i][j] != '1'){return;}grid[i][j] = '2';infect(grid, i + 1, j);infect(grid, i - 1, j);infect(grid, i, j + 1);infect(grid, i, j - 1);}
}