Number of Islands

標籤：

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:

11110110101100000000

Answer: 1

Example 2:

11000110000010000011

Answer: 3

簡單的dfs

class Solution{public:    bool vis[1000][1000];    int m,n;    void dfs(vector<vector<char>>&grid, int x, int y){        if(x < 0 || y < 0 || x >= m || y >= n || vis[x][y]) return;            vis[x][y] = 1;        if(grid[x][y] == '1'){        dfs(grid,x+1,y);        dfs(grid,x-1,y);        dfs(grid,x,y+1);        dfs(grid,x,y-1);        }    }    int numIslands(vector<vector<char>> &grid){        int cnt = 0;        if(grid.size() == 0) return cnt;        m = grid.size();        n = grid[0].size();       memset(vis,0,sizeof(vis));        for(int i = 0; i < grid.size(); i++)         for(int j = 0; j < grid[0].size(); j++)        if(!vis[i][j] && grid[i][j] == '1'){              dfs(grid,i,j);              cnt++;        }        return cnt;    }};

Number of Islands