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			35 lines
		
	
	
		
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			35 lines
		
	
	
		
			1.3 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
<p>There exists an infinitely large two-dimensional grid of uncolored unit cells. You are given a positive integer <code>n</code>, indicating that you must do the following routine for <code>n</code> minutes:</p>
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<ul>
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	<li>At the first minute, color <strong>any</strong> arbitrary unit cell blue.</li>
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	<li>Every minute thereafter, color blue <strong>every</strong> uncolored cell that touches a blue cell.</li>
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</ul>
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<p>Below is a pictorial representation of the state of the grid after minutes 1, 2, and 3.</p>
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<img alt="" src="https://assets.leetcode.com/uploads/2023/01/10/example-copy-2.png" style="width: 500px; height: 279px;" />
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<p>Return <em>the number of <strong>colored cells</strong> at the end of </em><code>n</code> <em>minutes</em>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> n = 1
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> After 1 minute, there is only 1 blue cell, so we return 1.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> n = 2
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<strong>Output:</strong> 5
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<strong>Explanation:</strong> After 2 minutes, there are 4 colored cells on the boundary and 1 in the center, so we return 5. 
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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>1 <= n <= 10<sup>5</sup></code></li>
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</ul>
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