LeetCode-Number of Islands-解题报告

原题链接 https://leetcode.com/problems/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

以前刷acm题的时候遇到过类似的， 用fillflood就可以解决。

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
		int cnt = 0;
		for (int i = 0; i < grid.size(); ++i)
		{
			for (int j = 0; j < grid[i].size(); ++j)
			{
				if (grid[i][j] == '1')
				{
					dfs(grid, i, j, 'a');
					cnt++;
				}
			}
		}
		return cnt;
	}
	void dfs(vector<vector<char>>& grid, int i, int j, char color)
	{
		if (i < 0 || j < 0 || j >= grid[0].size() || i >= grid.size())return;
		if (grid[i][j] != '1')return;
		grid[i][j] = color;
		dfs(grid, i + 1, j, color);
		dfs(grid, i - 1, j, color);
		dfs(grid, i, j + 1, color);
		dfs(grid, i, j - 1, color);
	}
};