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51 lines
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51 lines
2.8 KiB
HTML
<p>We have a wooden plank of the length <code>n</code> <strong>units</strong>. Some ants are walking on the plank, each ant moves with a speed of <strong>1 unit per second</strong>. Some of the ants move to the <strong>left</strong>, the other move to the <strong>right</strong>.</p>
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<p>When two ants moving in two <strong>different</strong> directions meet at some point, they change their directions and continue moving again. Assume changing directions does not take any additional time.</p>
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<p>When an ant reaches <strong>one end</strong> of the plank at a time <code>t</code>, it falls out of the plank immediately.</p>
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<p>Given an integer <code>n</code> and two integer arrays <code>left</code> and <code>right</code>, the positions of the ants moving to the left and the right, return <em>the moment when the last ant(s) fall out of the plank</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/06/17/ants.jpg" style="width: 450px; height: 610px;" />
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<pre>
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<strong>Input:</strong> n = 4, left = [4,3], right = [0,1]
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<strong>Output:</strong> 4
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<strong>Explanation:</strong> In the image above:
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-The ant at index 0 is named A and going to the right.
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-The ant at index 1 is named B and going to the right.
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-The ant at index 3 is named C and going to the left.
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-The ant at index 4 is named D and going to the left.
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The last moment when an ant was on the plank is t = 4 seconds. After that, it falls immediately out of the plank. (i.e., We can say that at t = 4.0000000001, there are no ants on the plank).
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</pre>
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<p><strong>Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/06/17/ants2.jpg" style="width: 639px; height: 101px;" />
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<pre>
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<strong>Input:</strong> n = 7, left = [], right = [0,1,2,3,4,5,6,7]
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<strong>Output:</strong> 7
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<strong>Explanation:</strong> All ants are going to the right, the ant at index 0 needs 7 seconds to fall.
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</pre>
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<p><strong>Example 3:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/06/17/ants3.jpg" style="width: 639px; height: 100px;" />
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<pre>
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<strong>Input:</strong> n = 7, left = [0,1,2,3,4,5,6,7], right = []
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<strong>Output:</strong> 7
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<strong>Explanation:</strong> All ants are going to the left, the ant at index 7 needs 7 seconds to fall.
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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>4</sup></code></li>
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<li><code>0 <= left.length <= n + 1</code></li>
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<li><code>0 <= left[i] <= n</code></li>
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<li><code>0 <= right.length <= n + 1</code></li>
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<li><code>0 <= right[i] <= n</code></li>
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<li><code>1 <= left.length + right.length <= n + 1</code></li>
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<li>All values of <code>left</code> and <code>right</code> are unique, and each value can appear <strong>only in one</strong> of the two arrays.</li>
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</ul>
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