"content":"<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>\n\n<p>The class has three public methods:</p>\n\n<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>\n\n<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>\n\n<p><code>count()</code>: returns the count of un-expired keys.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> \nactions = ["TimeLimitedCache", "set", "get", "count", "get"]\nvalues = [[], [1, 42, 100], [1], [], [1]]\ntimeDelays = [0, 0, 50, 50, 150]\n<strong>Output:</strong> [null, false, 42, 1, -1]\n<strong>Explanation:</strong>\nAt t=0, the cache is constructed.\nAt 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.\nAt t=50, key=1 is requested and the value of 42 is returned.\nAt t=50, count() is called and there is one active key in the cache.\nAt t=100, key=1 expires.\nAt t=150, get(1) is called but -1 is returned because the cache is empty.\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> \nactions = ["TimeLimitedCache", "set", "set", "get", "get", "get", "count"]\nvalues = [[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []]\ntimeDelays = [0, 0, 40, 50, 120, 200, 250]\n<strong>Output:</strong> [null, false, true, 50, 50, -1, 0]\n<strong>Explanation:</strong>\nAt t=0, the cache is constructed.\nAt 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.\nAt 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.\nAt t=50, get(1) is called which returned 50.\nAt t=120, get(1) is called which returned 50.\nAt t=140, key=1 expires.\nAt t=200, get(1) is called but the cache is empty so -1 is returned.\nAt t=250, count() returns 0 because the cache is empty.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= key, value <= 10<sup>9</sup></code></li>\n\t<li><code>0 <= duration <= 1000</code></li>\n\t<li><code>1 <= actions.length <= 100</code></li>\n\t<li><code>actions.length === values.length</code></li>\n\t<li><code>actions.length === timeDelays.length</code></li>\n\t<li><code>0 <= timeDelays[i] <= 1450</code></li>\n\t<li><code>actions[i]</code> is one of "TimeLimitedCache", "set", "get" and "count"</li>\n\t<li>First action is always "TimeLimitedCache" and must be executed immediately, with a 0-millisecond delay</li>\n</ul>\n",
"You can delay execution of code with \"ref = setTimeout(fn, delay)\". You can abort the execution with \"clearTimeout(ref)\"",
"When storing the values in the cache, also store a reference to the timeout. The timeout should clear the key from the cache after the expiration has elapsed.",
"When you set a key that already exists, clear the existing timeout."
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