mirror of
https://gitee.com/coder-xiaomo/leetcode-problemset
synced 2025-01-11 02:58:13 +08:00
57 lines
2.9 KiB
HTML
57 lines
2.9 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>
|
|
|
|
<p>The class has three public methods:</p>
|
|
|
|
<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>
|
|
|
|
<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>
|
|
|
|
<p><code>count()</code>: returns the count of un-expired keys.</p>
|
|
|
|
<p> </p>
|
|
<p><strong class="example">Example 1:</strong></p>
|
|
|
|
<pre>
|
|
<strong>Input:</strong>
|
|
["TimeLimitedCache", "set", "get", "count", "get"]
|
|
[[], [1, 42, 100], [1], [], [1]]
|
|
[0, 0, 50, 50, 150]
|
|
<strong>Output:</strong> [null, false, 42, 1, -1]
|
|
<strong>Explanation:</strong>
|
|
At t=0, the cache is constructed.
|
|
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.
|
|
At t=50, key=1 is requested and the value of 42 is returned.
|
|
At t=50, count() is called and there is one active key in the cache.
|
|
At t=100, key=1 expires.
|
|
At t=150, get(1) is called but -1 is returned because the cache is empty.
|
|
</pre>
|
|
|
|
<p><strong class="example">Example 2:</strong></p>
|
|
|
|
<pre>
|
|
<strong>Input:</strong>
|
|
["TimeLimitedCache", "set", "set", "get", "get", "get", "count"]
|
|
[[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []]
|
|
[0, 0, 40, 50, 120, 200, 250]
|
|
<strong>Output:</strong> [null, false, true, 50, 50, -1]
|
|
<strong>Explanation:</strong>
|
|
At t=0, the cache is constructed.
|
|
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.
|
|
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.
|
|
At t=50, get(1) is called which returned 50.
|
|
At t=120, get(1) is called which returned 50.
|
|
At t=140, key=1 expires.
|
|
At t=200, get(1) is called but the cache is empty so -1 is returned.
|
|
At t=250, count() returns 0 because the cache is empty.
|
|
</pre>
|
|
|
|
<p> </p>
|
|
<p><strong>Constraints:</strong></p>
|
|
|
|
<ul>
|
|
<li><code>0 <= key <= 10<sup>9</sup></code></li>
|
|
<li><code>0 <= value <= 10<sup>9</sup></code></li>
|
|
<li><code>0 <= duration <= 1000</code></li>
|
|
<li><code>total method calls will not exceed 100</code></li>
|
|
</ul>
|