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55 lines
2.8 KiB
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55 lines
2.8 KiB
HTML
<p>There are <code>n</code> cars going to the same destination along a one-lane road. The destination is <code>target</code> miles away.</p>
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<p>You are given two integer array <code>position</code> and <code>speed</code>, both of length <code>n</code>, where <code>position[i]</code> is the position of the <code>i<sup>th</sup></code> car and <code>speed[i]</code> is the speed of the <code>i<sup>th</sup></code> car (in miles per hour).</p>
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<p>A car can never pass another car ahead of it, but it can catch up to it and drive bumper to bumper <strong>at the same speed</strong>. The faster car will <strong>slow down</strong> to match the slower car's speed. The distance between these two cars is ignored (i.e., they are assumed to have the same position).</p>
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<p>A <strong>car fleet</strong> is some non-empty set of cars driving at the same position and same speed. Note that a single car is also a car fleet.</p>
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<p>If a car catches up to a car fleet right at the destination point, it will still be considered as one car fleet.</p>
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<p>Return <em>the <strong>number of car fleets</strong> that will arrive at the destination</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> target = 12, position = [10,8,0,5,3], speed = [2,4,1,1,3]
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<strong>Output:</strong> 3
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<strong>Explanation:</strong>
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The cars starting at 10 (speed 2) and 8 (speed 4) become a fleet, meeting each other at 12.
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The car starting at 0 does not catch up to any other car, so it is a fleet by itself.
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The cars starting at 5 (speed 1) and 3 (speed 3) become a fleet, meeting each other at 6. The fleet moves at speed 1 until it reaches target.
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Note that no other cars meet these fleets before the destination, so the answer is 3.
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> target = 10, position = [3], speed = [3]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> There is only one car, hence there is only one fleet.
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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> target = 100, position = [0,2,4], speed = [4,2,1]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong>
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The cars starting at 0 (speed 4) and 2 (speed 2) become a fleet, meeting each other at 4. The fleet moves at speed 2.
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Then, the fleet (speed 2) and the car starting at 4 (speed 1) become one fleet, meeting each other at 6. The fleet moves at speed 1 until it reaches target.
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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>n == position.length == speed.length</code></li>
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<li><code>1 <= n <= 10<sup>5</sup></code></li>
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<li><code>0 < target <= 10<sup>6</sup></code></li>
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<li><code>0 <= position[i] < target</code></li>
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<li>All the values of <code>position</code> are <strong>unique</strong>.</li>
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<li><code>0 < speed[i] <= 10<sup>6</sup></code></li>
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</ul>
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