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Description
tab: English
<p>Given an <code>m x n</code> 2D binary grid <code>grid</code> which represents a map of <code>'1'</code>s (land) and <code>'0'</code>s (water), return <em>the number of islands</em>.</p>
<p>An <strong>island</strong> 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.</p>
<p> </p>
<p><strong class="example">Example 1:</strong></p>
<pre>
<strong>Input:</strong> grid = [
["1","1","1","1","0"],
["1","1","0","1","0"],
["1","1","0","0","0"],
["0","0","0","0","0"]
]
<strong>Output:</strong> 1
</pre>
<p><strong class="example">Example 2:</strong></p>
<pre>
<strong>Input:</strong> grid = [
["1","1","0","0","0"],
["1","1","0","0","0"],
["0","0","1","0","0"],
["0","0","0","1","1"]
]
<strong>Output:</strong> 3
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<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> is <code>'0'</code> or <code>'1'</code>.</li>
</ul>
---
[submissions](https://leetcode.com/problems/number-of-islands/submissions/) | [solutions](https://leetcode.com/problems/number-of-islands/solutions/)
tab: 中文
<p>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。</p>
<p>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。</p>
<p>此外，你可以假设该网格的四条边均被水包围。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>grid = [
['1','1','1','1','0'],
['1','1','0','1','0'],
['1','1','0','0','0'],
['0','0','0','0','0']
]
<strong>输出：</strong>1
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>grid = [
['1','1','0','0','0'],
['1','1','0','0','0'],
['0','0','1','0','0'],
['0','0','0','1','1']
]
<strong>输出：</strong>3
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<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>
---
[提交记录](https://leetcode.cn/problems/number-of-islands/submissions/) | [题解](https://leetcode.cn/problems/number-of-islands/solution/)
Solutions & Notes
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