public class NumIslands_200 {

/**

* 使用深度优先遍历来求解（DFS）

* @param grid

* @return

*/

public static int numIslands(char[][] grid) {

int result = 0;

for (int i = 0; i < grid.length; i++) {

for (int j = 0; j < grid[0].length; j++) {

// 遍历二维数组

if (grid[i][j] != '0') {

dfs(grid, i, j);

result++;

}

}

}

return result;

}

private static void dfs(char[][] grid, int i, int j) {

// 递归终止条件

if(i >= grid.length || i < 0 || j >= grid[0].length || j < 0 || grid[i][j] == '0') {

return;

}

// 遍历过的元素置为0，防止重复遍历

grid[i][j] = '0';

dfs(grid, i - 1, j);

dfs(grid, i + 1, j);

dfs(grid, i, j + 1);

dfs(grid, i, j - 1);

}

public static void main(String[] args) {

char[][] grid = {{'1','1','0','0','0'},{'1','1','0','0','0'},{'0','0','1','0','0'},{'0','0','0','1','1'}};

System.out.println(numIslands(grid));

}

}