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48 lines
3.1 KiB
HTML
<p>You are given a <strong>0-indexed</strong> <code>m x n</code> binary matrix <code>land</code> where a <code>0</code> represents a hectare of forested land and a <code>1</code> represents a hectare of farmland.</p>
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<p>To keep the land organized, there are designated rectangular areas of hectares that consist <strong>entirely</strong> of farmland. These rectangular areas are called <strong>groups</strong>. No two groups are adjacent, meaning farmland in one group is <strong>not</strong> four-directionally adjacent to another farmland in a different group.</p>
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<p><code>land</code> can be represented by a coordinate system where the top left corner of <code>land</code> is <code>(0, 0)</code> and the bottom right corner of <code>land</code> is <code>(m-1, n-1)</code>. Find the coordinates of the top left and bottom right corner of each <strong>group</strong> of farmland. A <strong>group</strong> of farmland with a top left corner at <code>(r<sub>1</sub>, c<sub>1</sub>)</code> and a bottom right corner at <code>(r<sub>2</sub>, c<sub>2</sub>)</code> is represented by the 4-length array <code>[r<sub>1</sub>, c<sub>1</sub>, r<sub>2</sub>, c<sub>2</sub>].</code></p>
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<p>Return <em>a 2D array containing the 4-length arrays described above for each <strong>group</strong> of farmland in </em><code>land</code><em>. If there are no groups of farmland, return an empty array. You may return the answer in <strong>any order</strong></em>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-23-15-copy-of-diagram-drawio-diagrams-net.png" style="width: 300px; height: 300px;" />
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<pre>
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<strong>Input:</strong> land = [[1,0,0],[0,1,1],[0,1,1]]
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<strong>Output:</strong> [[0,0,0,0],[1,1,2,2]]
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<strong>Explanation:</strong>
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The first group has a top left corner at land[0][0] and a bottom right corner at land[0][0].
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The second group has a top left corner at land[1][1] and a bottom right corner at land[2][2].
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-30-26-copy-of-diagram-drawio-diagrams-net.png" style="width: 200px; height: 200px;" />
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<pre>
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<strong>Input:</strong> land = [[1,1],[1,1]]
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<strong>Output:</strong> [[0,0,1,1]]
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<strong>Explanation:</strong>
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The first group has a top left corner at land[0][0] and a bottom right corner at land[1][1].
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-32-24-copy-of-diagram-drawio-diagrams-net.png" style="width: 100px; height: 100px;" />
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<pre>
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<strong>Input:</strong> land = [[0]]
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<strong>Output:</strong> []
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<strong>Explanation:</strong>
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There are no groups of farmland.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>m == land.length</code></li>
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<li><code>n == land[i].length</code></li>
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<li><code>1 <= m, n <= 300</code></li>
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<li><code>land</code> consists of only <code>0</code>'s and <code>1</code>'s.</li>
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<li>Groups of farmland are <strong>rectangular</strong> in shape.</li>
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</ul>
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