【DFS】200.岛屿数量

题目

法1：DFS

最简单的DFS必须掌握！！！

class Solution {public int numIslands(char[][] grid) {int m = grid.length, n = grid[0].length, ans = 0;if (m == 0 || n == 0) {return ans;}boolean[][] visited = new boolean[m][n];for (int i = 0; i < m; ++i) {for (int j = 0; j < n; ++j) {if (grid[i][j] == '1' && !visited[i][j]) {++ans;dfs(grid, visited, i, j);}}}return ans;}public void dfs(char[][] grid, boolean[][] visited, int i, int j) {if (i >= 0 && i < grid.length && j >= 0 && j < grid[0].length && grid[i][j] == '1' && !visited[i][j]) {visited[i][j] = true;dfs(grid, visited, i - 1, j);dfs(grid, visited, i + 1, j);dfs(grid, visited, i, j + 1);dfs(grid, visited, i, j - 1);}}
}