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61 lines
3.3 KiB
HTML
61 lines
3.3 KiB
HTML
<p>Write a class that allows getting and setting key-value pairs, however a <strong>time until expiration</strong> is associated with each key.</p>
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<p>The class has three public methods:</p>
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<p><code>set(key, value, duration)</code>: accepts an integer <code>key</code>, an integer <code>value</code>, and a <code>duration</code> in milliseconds. Once the <code>duration</code> has elapsed, the key should be inaccessible. The method should return <code>true</code> if the same un-expired key already exists and <code>false</code> otherwise. Both the value and duration should be overwritten if the key already exists.</p>
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<p><code>get(key)</code>: if an un-expired key exists, it should return the associated value. Otherwise it should return <code>-1</code>.</p>
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<p><code>count()</code>: returns the count of un-expired keys.</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>
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actions = ["TimeLimitedCache", "set", "get", "count", "get"]
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values = [[], [1, 42, 100], [1], [], [1]]
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timeDelays = [0, 0, 50, 50, 150]
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<strong>Output:</strong> [null, false, 42, 1, -1]
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<strong>Explanation:</strong>
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At t=0, the cache is constructed.
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At t=0, a key-value pair (1: 42) is added with a time limit of 100ms. The value doesn't exist so false is returned.
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At t=50, key=1 is requested and the value of 42 is returned.
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At t=50, count() is called and there is one active key in the cache.
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At t=100, key=1 expires.
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At t=150, get(1) is called but -1 is returned because the cache is empty.
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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>
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actions = ["TimeLimitedCache", "set", "set", "get", "get", "get", "count"]
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values = [[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []]
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timeDelays = [0, 0, 40, 50, 120, 200, 250]
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<strong>Output:</strong> [null, false, true, 50, 50, -1, 0]
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<strong>Explanation:</strong>
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At t=0, the cache is constructed.
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At t=0, a key-value pair (1: 42) is added with a time limit of 50ms. The value doesn't exist so false is returned.
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At t=40, a key-value pair (1: 50) is added with a time limit of 100ms. A non-expired value already existed so true is returned and the old value was overwritten.
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At t=50, get(1) is called which returned 50.
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At t=120, get(1) is called which returned 50.
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At t=140, key=1 expires.
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At t=200, get(1) is called but the cache is empty so -1 is returned.
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At t=250, count() returns 0 because the cache is empty.
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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>0 <= key, value <= 10<sup>9</sup></code></li>
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<li><code>0 <= duration <= 1000</code></li>
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<li><code>1 <= actions.length <= 100</code></li>
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<li><code>actions.length === values.length</code></li>
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<li><code>actions.length === timeDelays.length</code></li>
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<li><code>0 <= timeDelays[i] <= 1450</code></li>
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<li><code>actions[i]</code> is one of "TimeLimitedCache", "set", "get" and "count"</li>
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<li>First action is always "TimeLimitedCache" and must be executed immediately, with a 0-millisecond delay</li>
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</ul>
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