Cache with time limit

76.0% acceptance

Mar 2, 2026

531

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.

Solution

TypeScript

Time O(n)

Space O(1)

LeetCode

solution.ts

class TimeLimitedCache {
  private cache: Map<number, { value: number; expiry: number }>;

  constructor() {
  this.cache = new Map();
  }

  set(key: number, value: number, duration: number): boolean {
  const now = Date.now();
  const exists = this.cache.has(key) && this.cache.get(key)!.expiry > now;
  this.cache.set(key, { value, expiry: now + duration });
  return exists;
  }

  get(key: number): number {
  const now = Date.now();
  const entry = this.cache.get(key);
  if (entry && entry.expiry > now) return entry.value;
  return -1;
  }

  count(): number {
  const now = Date.now();
  let count = 0;
  for (const entry of this.cache.values()) {
    if (entry.expiry > now) count++;
  }
  return count;
  }
}

/**
 * const timeLimitedCache = new TimeLimitedCache()
 * timeLimitedCache.set(1, 42, 1000); // false
 * timeLimitedCache.get(1) // 42
 * timeLimitedCache.count() // 1
 */