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| 1 | +package data_structure; |
| 2 | + |
| 3 | +import java.util.HashMap; |
| 4 | +import java.util.Map; |
| 5 | + |
| 6 | +public class LRUCache { |
| 7 | + |
| 8 | + static class Node { |
| 9 | + int key; |
| 10 | + int value; |
| 11 | + Node next; |
| 12 | + Node prev; |
| 13 | + |
| 14 | + public Node(int key, int value) { |
| 15 | + this.key = key; |
| 16 | + this.value = value; |
| 17 | + } |
| 18 | + } |
| 19 | + |
| 20 | + private final Map<Integer, Node> nodeMap; |
| 21 | + private final Node head; |
| 22 | + private final Node tail; |
| 23 | + private final int capacity; |
| 24 | + |
| 25 | + public LRUCache(int capacity) { |
| 26 | + this.nodeMap = new HashMap<>(); |
| 27 | + this.capacity = capacity; |
| 28 | + this.head = new Node(-1, -1); |
| 29 | + this.tail = new Node(-1, -1); |
| 30 | + head.next = tail; |
| 31 | + tail.prev = head; |
| 32 | + } |
| 33 | + |
| 34 | + /* |
| 35 | + * insert |
| 36 | + * */ |
| 37 | + public void add(int key, int value) { |
| 38 | + if (nodeMap.containsKey(key)) { |
| 39 | + Node node = nodeMap.get(key); |
| 40 | + node.value = value; |
| 41 | + moveToFront(node); |
| 42 | + } else { |
| 43 | + Node node = new Node(key, value); |
| 44 | + insertToFront(node); |
| 45 | + nodeMap.put(node.key, node); |
| 46 | + |
| 47 | + if (capacity < nodeMap.size()) { |
| 48 | + removeLRU(); |
| 49 | + } |
| 50 | + } |
| 51 | + } |
| 52 | + |
| 53 | + private void moveToFront(Node node) { |
| 54 | + cutChain(node); |
| 55 | + insertToFront(node); |
| 56 | + } |
| 57 | + |
| 58 | + private void insertToFront(Node node) { |
| 59 | + Node next = head.next; |
| 60 | + next.prev = node; |
| 61 | + head.next = node; |
| 62 | + } |
| 63 | + |
| 64 | + private void cutChain(Node node) { |
| 65 | + Node prev = node.prev; |
| 66 | + Node next = node.next; |
| 67 | + prev.next = next; |
| 68 | + next.prev = prev; |
| 69 | + } |
| 70 | + |
| 71 | + private void removeLRU() { |
| 72 | + Node last = tail.prev; |
| 73 | + Node prev = last.prev; |
| 74 | + prev.next = tail; |
| 75 | + tail.prev = prev; |
| 76 | + nodeMap.remove(last.key); |
| 77 | + } |
| 78 | + |
| 79 | + /* |
| 80 | + * get |
| 81 | + * */ |
| 82 | + public int get(int key) { |
| 83 | + if (!nodeMap.containsKey(key)) { |
| 84 | + return -1; |
| 85 | + } |
| 86 | + Node node = nodeMap.get(key); |
| 87 | + moveToFront(node); |
| 88 | + return node.value; |
| 89 | + } |
| 90 | + |
| 91 | + /* |
| 92 | + * delete |
| 93 | + * */ |
| 94 | + public void evict(int key) { |
| 95 | + if (!nodeMap.containsKey(key)) { |
| 96 | + return; |
| 97 | + } |
| 98 | + Node node = nodeMap.get(key); |
| 99 | + cutChain(node); |
| 100 | + nodeMap.remove(key); |
| 101 | + } |
| 102 | + |
| 103 | + /* |
| 104 | + * for test |
| 105 | + * */ |
| 106 | + public void print() { |
| 107 | + System.out.println("size : " + nodeMap.size()); |
| 108 | + for (Map.Entry<Integer, Node> node : nodeMap.entrySet()) { |
| 109 | + System.out.println("key : %s, value : %s".formatted(node.getKey(), node.getValue().value)); |
| 110 | + } |
| 111 | + } |
| 112 | + |
| 113 | + public static void main(String[] args) { |
| 114 | + LRUCache lruCache = new LRUCache(3); |
| 115 | + lruCache.add(1, 10); |
| 116 | + lruCache.add(2, 11); |
| 117 | + lruCache.add(3, 8); |
| 118 | + lruCache.print(); |
| 119 | + |
| 120 | + lruCache.add(5, 11); |
| 121 | + lruCache.print(); |
| 122 | + |
| 123 | + lruCache.add(2, 14); |
| 124 | + lruCache.print(); |
| 125 | + |
| 126 | + lruCache.get(3); |
| 127 | + lruCache.add(7, 99); |
| 128 | + lruCache.print(); |
| 129 | + } |
| 130 | +} |
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