53 lines
1.2 KiB
Dart
53 lines
1.2 KiB
Dart
import 'dart:collection';
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class LRUCache<K, V> {
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int _capacity;
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final LinkedHashMap<K, V> _cache;
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LRUCache(
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this._capacity, {
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bool Function(K, K)? equals,
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int Function(K)? hashCode,
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bool Function(dynamic)? isValidKey,
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}) : _cache = LinkedHashMap<K, V>(
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equals: equals,
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hashCode: hashCode,
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isValidKey: isValidKey,
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);
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void resize(int capacity) {
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if (_capacity > capacity) {
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_cache.keys.take(_capacity - capacity).forEach(_cache.remove);
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}
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_capacity = capacity;
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}
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bool contains(K key) {
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return _cache.containsKey(key);
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}
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V? get(K key) {
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final value = _cache.remove(key); // Temporarily remove the item.
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if (value != null) {
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_cache[key] =
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value; // Re-inserting the item makes it the most-recently used.
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}
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return value;
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}
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V set(K key, V value) {
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if (_cache.containsKey(key)) {
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_cache.remove(key); // Remove the existing item before updating.
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} else if (_cache.length == _capacity) {
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_cache.remove(
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_cache.keys.first,
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); // Explicitly remove the least recently used item if at capacity.
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}
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return _cache[key] = value; // Inserting or updating the item.
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}
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}
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