题目描述

• 直接毁岛！
• 每次发现一个岛，ans++，然后直接把整个岛毁了（感染）
• 直到最后，找出所有岛，此时地图上全都是’0’
  

代码 & 思路

• 每次找到一个岛，就进行四个方向的递归感染，把整个岛都毁了。

class Solution {int m;int n;public int numIslands(char[][] grid) {m = grid.length;n = grid[0].length;int ans = 0;for(int i=0;i<m;i++){for(int j=0;j<n;j++){// 答案加一，然后把岛毁了if(grid[i][j] == '1'){ans++;dfs(grid,i,j);}}}return ans;}void dfs(char[][] grid, int i, int j){if(i < m && j < n && i >= 0 && j >= 0){if(grid[i][j] == '1'){grid[i][j] = '0';dfs(grid,i+1,j);dfs(grid,i,j+1);dfs(grid,i-1,j);dfs(grid,i,j-1);}}}
}

更新代码

class Solution {public int numIslands(char[][] grid) {int counts = 0;for(int i = 0; i < grid.length; i++) {for(int j = 0; j < grid[0].length; j++) {if(grid[i][j] == '1') {counts++;fire(grid, i, j);}}}return counts;}public void fire(char[][] grid, int i, int j) {if(i >= grid.length || j >= grid[0].length || i < 0 || j < 0 || grid[i][j] == '0') {return;}grid[i][j] = '0';fire(grid, i + 1, j);fire(grid, i - 1, j);fire(grid, i, j + 1);fire(grid, i, j - 1);}
}