Number of Islands

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Example 1:

11110
11010
11000
00000

Answer: 1

Example 2:

11000
11000
00100
00011

Answer: 3

一道dfs的题，思路是按照顺序扫，碰到1说明出现了小岛，那么吧与他相临的1全部置为0，这样能够保证这一片统计出来只有一个岛。

代码：

public int numIslands(char[][] grid) {        int count = 0;        for(int i=0;i<grid.length;i++){            for(int j=0;j<grid[0].length;j++){                if(grid[i][j] == '1'){                    //grid[i][j] = '0';                    count++;                    bfs(grid, i, j);                }            }        }        return count;    }    public void dfs(char[][] grid, int i, int j){        if(grid[i][j] == '1'){            grid[i][j] = '0';            if(i>0){                dfs(grid, i-1, j);            }            if(i<grid.length-1){                dfs(grid, i+1, j);            }            if(j>0){                dfs(grid, i, j-1);            }            if(j<grid[0].length-1){                dfs(grid, i, j+1);            }        }    }