LeetCode-Number of Islands-解題報告

原題鏈接 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題的時候遇到過類似的， 用fillflood就可以解決。

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);
	}
};