postApril 14, 2026

LRU Cache Implementation

#javascript#map#cache#data-structures#algorithms

Hard⏱️ Logic Challenge

Implement an LRUCache class with get(key) and put(key, value) operations, both O(1). When capacity is exceeded, evict the least recently used item.

Ver solución

class LRUCache {
  constructor(capacity) {
    this.cap = capacity;
    this.map = new Map();  // JS Map maintains insertion order
  }
  get(key) {
    if (!this.map.has(key)) return -1;
    const val = this.map.get(key);
    this.map.delete(key);
    this.map.set(key, val);  // move to end (most recent)
    return val;
  }
  put(key, value) {
    this.map.delete(key);
    this.map.set(key, value);
    if (this.map.size > this.cap) {
      this.map.delete(this.map.keys().next().value); // evict first = LRU
    }
  }
}

// Map.keys().next().value = the oldest inserted key.
// Delete + re-insert on access moves item to 'most recent'.