least-frequently-used/dist/index.js

Implementation of LFU from Leetcode with tests

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.LFUCache = void 0;
class LFUCache {
    constructor(capacity) {
        this.cache = new Map();
        this.frequencies = new Map();
        this.minFrequency = 1;
        this.capacity = capacity;
    }
    get(key) {
        if (!this.cache.has(key)) {
            return -1;
        }
        const record = this.cache.get(key);
        if (!record) {
            return -1;
        }
        record.frequency = record.frequency + 1;
        this.updateFrequency(record.frequency, key);
        return record.value;
    }
    updateFrequency(frequencyKey, key) {
        const oldFr = frequencyKey - 1;
        const oldSet = this.frequencies.get(oldFr);
        if (oldSet) {
            oldSet.delete(key);
        }
        if (this.frequencies.has(frequencyKey)) {
            const frequency = this.frequencies.get(frequencyKey);
            if (frequency) {
                frequency.add(key);
            }
        }
        else {
            this.frequencies.set(frequencyKey, (new Set()).add(key));
        }
        if (frequencyKey < this.minFrequency || (oldSet && !oldSet.size && oldFr === this.minFrequency)) {
            this.minFrequency = frequencyKey;
        }
    }
    put(key, value) {
        if (this.capacity === 0) {
            return;
        }
        if (this.cache.has(key)) {
            const record = this.cache.get(key);
            if (!record) {
                return;
            }
            record.frequency = record.frequency + 1;
            record.value = value;
            this.updateFrequency(record.frequency, key);
        }
        else {
            if (this.cache.size === this.capacity) {
                const frequency = this.frequencies.get(this.minFrequency);
                if (!frequency) {
                    return;
                }
                const [firstKey] = frequency.values();
                this.cache.delete(firstKey);
                frequency.delete(firstKey);
                this.minFrequency = 1;
            }
            this.cache.set(key, { value: value, frequency: 1 });
            this.updateFrequency(1, key);
        }
    }
}
exports.LFUCache = LFUCache;