LeetCode-in-Java

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

Solution

class TimeLimitedCache {
    private readonly keyMap: Map<number, any>
    constructor() {
        this.keyMap = new Map<number, any>()
    }

    set(key: number, value: number, duration: number): boolean {
        let existed: boolean = this.keyMap.has(key)
        if (existed) clearTimeout(this.keyMap.get(key).clearRef)

        this.keyMap.set(key, {
            value,
            clearRef: setTimeout(() => {
                this.keyMap.delete(key)
            }, duration),
        })
        return existed
    }

    get(key: number): number {
        return this.keyMap.has(key) ? this.keyMap.get(key).value : -1
    }

    count(): number {
        return this.keyMap.size
    }
}

/*
 * Your TimeLimitedCache object will be instantiated and called as such:
 * var obj = new TimeLimitedCache()
 * obj.set(1, 42, 1000); // false
 * obj.get(1) // 42
 * obj.count() // 1
 */

export { TimeLimitedCache }

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