number-of-islands

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Algorithms

Given an <code>m x n</code> 2D binary grid <code>grid</code> which represents a map of <code>&#39;1&#39;</code>s (land) and <code>&#39;0&#39;</code>s (water), return 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.

&nbsp;
Example 1:

<pre>
Input: grid = [
 [&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;0&quot;],
 [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;],
 [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
 [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;]
]
Output: 1
</pre>

Example 2:

<pre>
Input: grid = [
 [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
 [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
 [&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],
 [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;]
]
Output: 3
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 300</code></li>
	<li><code>grid[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

numIslands

Number of Islands

Surrounded Regions

surrounded-regions

被围绕的区域

Walls and Gates

walls-and-gates

墙与门

Number of Islands II

number-of-islands-ii

岛屿数量 II

Number of Connected Components in an Undirected Graph

number-of-connected-components-in-an-undirected-graph

无向图中连通分量的数目

Battleships in a Board

battleships-in-a-board

棋盘上的战舰

Number of Distinct Islands

number-of-distinct-islands

不同岛屿的数量

Max Area of Island

max-area-of-island

岛屿的最大面积

Count Sub Islands

count-sub-islands

统计子岛屿

Find All Groups of Farmland

find-all-groups-of-farmland

找到所有的农场组

Count Unreachable Pairs of Nodes in an Undirected Graph

count-unreachable-pairs-of-nodes-in-an-undirected-graph

统计无向图中无法互相到达点对数

Maximum Number of Fish in a Grid

maximum-number-of-fish-in-a-grid

网格图中鱼的最大数目

Depth-First Search

Breadth-First Search

Union Find

Array

Matrix

给你一个由 <code>'1'</code>（陆地）和 <code>'0'</code>（水）组成的的二维网格，请你计算网格中岛屿的数量。

岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。

此外，你可以假设该网格的四条边均被水包围。

 

示例 1：

<pre>
输入：grid = [
 ["1","1","1","1","0"],
 ["1","1","0","1","0"],
 ["1","1","0","0","0"],
 ["0","0","0","0","0"]
]
输出：1
</pre>

示例 2：

<pre>
输入：grid = [
 ["1","1","0","0","0"],
 ["1","1","0","0","0"],
 ["0","0","1","0","0"],
 ["0","0","0","1","1"]
]
输出：3
</pre>

 

提示：

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 <= m, n <= 300</code></li>
	<li><code>grid[i][j]</code> 的值为 <code>'0'</code> 或 <code>'1'</code></li>
</ul>