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g2601_2700.s2622_cache_with_time_limit.readme.md Maven / Gradle / Ivy

2622\. Cache With Time Limit

Medium

Write a class that allows getting and setting key-value pairs, however a **time until expiration** is associated with each key.

The class has three public methods:

`set(key, value, duration)`: accepts an integer `key`, an integer `value`, and a `duration` in milliseconds. Once the `duration` has elapsed, the key should be inaccessible. The method should return `true` if the same un-expired key already exists and `false` otherwise. Both the value and duration should be overwritten if the key already exists.

`get(key)`: if an un-expired key exists, it should return the associated value. Otherwise it should return `-1`.

`count()`: returns the count of un-expired keys.

**Example 1:**

**Input:** ["TimeLimitedCache", "set", "get", "count", "get"] [[], [1, 42, 100], [1], [], [1]] [0, 0, 50, 50, 150]

**Output:** [null, false, 42, 1, -1]

**Explanation:** 

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.

**Example 2:**

**Input:** ["TimeLimitedCache", "set", "set", "get", "get", "get", "count"] [[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []] [0, 0, 40, 50, 120, 200, 250]

**Output:** [null, false, true, 50, 50, -1]

**Explanation:** 

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.

**Constraints:**

*   0 <= key <= 109
*   0 <= value <= 109
*   `0 <= duration <= 1000`
*   `total method calls will not exceed 100`