程序员人生网站导航

[LeetCode] Number of Islands

栏目：php教程时间：2015-06-04 08:12:49

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:

Answer: 1

Example 2:

Answer: 3

解题思路

深度优先搜索，要求的结果就是图中连通份量的个数。更详细的思路可以参考Find the number of islands。

实现代码

//Runtime:13ms
class Solution {
public:
    int numIslands(vector<vector<char>> &grid) {
        if (grid.empty() || grid[0].empty()) return 0;
        int row = grid.size();
        int col = grid[0].size();
        int cnt = 0;
        for (int i = 0; i < row; i++)
        {
            for (int j = 0; j < col; j++)
            {
                if (grid[i][j] == '1')
                {
                    cnt++;
                    dfs(grid, i, j);
                }
            }
        }

        return cnt;
    }

private:
    void dfs(vector<vector<char>> &grid, int row, int col)
    {
        if (row < 0 || row >= grid.size() || col < 0 || col >= grid[0].size() || grid[row][col] != '1')
        {
            return;
        }

        grid[row][col] = 'X';
        dfs(grid, row, col + 1);
        dfs(grid, row + 1, col);
        dfs(grid, row, col - 1);
        dfs(grid, row - 1, col);
    }
};

------分隔线----------------------------

上一篇 IOS ---网络异步请求

下一篇 C++数组。

------分隔线----------------------------