|
| 1 | +class LinkedNode( |
| 2 | + val key: Int, |
| 3 | + var value: Int, |
| 4 | + var prev: LinkedNode?, |
| 5 | + var next: LinkedNode?, |
| 6 | +) |
| 7 | + |
| 8 | +class LRUCache(private val capacity: Int) { |
| 9 | + private val pointerByKey = hashMapOf<Int, LinkedNode>() |
| 10 | + private var lruKey: LinkedNode? = null // head |
| 11 | + private var mruKey: LinkedNode? = null // tail |
| 12 | + private var size = 0 |
| 13 | + |
| 14 | + fun get(key: Int): Int { |
| 15 | + val node = pointerByKey[key] |
| 16 | + node ?: return -1 |
| 17 | + |
| 18 | + val value = node.value |
| 19 | + |
| 20 | + // pointer comparison |
| 21 | + if (node !== mruKey) { |
| 22 | + node.prev?.next = node.next |
| 23 | + node.next?.prev = node.prev |
| 24 | + if (node === lruKey) { |
| 25 | + lruKey = node.next |
| 26 | + } |
| 27 | + |
| 28 | + mruKey!!.next = node |
| 29 | + node.prev = mruKey |
| 30 | + node.next = null |
| 31 | + mruKey = node |
| 32 | + } |
| 33 | + |
| 34 | + return value |
| 35 | + } |
| 36 | + |
| 37 | + fun put(key: Int, value: Int) { |
| 38 | + val cached = get(key) |
| 39 | + if (cached != -1) { |
| 40 | + mruKey!!.value = value |
| 41 | + return |
| 42 | + } |
| 43 | + |
| 44 | + if (size == capacity) { |
| 45 | + val removed = lruKey!! |
| 46 | + val newLruKey = removed.next |
| 47 | + |
| 48 | + pointerByKey.remove(removed.key) |
| 49 | + |
| 50 | + removed.next = null |
| 51 | + newLruKey?.prev = null |
| 52 | + |
| 53 | + lruKey = newLruKey |
| 54 | + } else { |
| 55 | + ++size |
| 56 | + } |
| 57 | + |
| 58 | + val newNode = LinkedNode( |
| 59 | + key = key, |
| 60 | + value = value, |
| 61 | + prev = mruKey, |
| 62 | + next = null, |
| 63 | + ) |
| 64 | + pointerByKey[key] = newNode |
| 65 | + |
| 66 | + if (lruKey == null) { |
| 67 | + lruKey = newNode |
| 68 | + } |
| 69 | + |
| 70 | + mruKey?.next = newNode |
| 71 | + mruKey = newNode |
| 72 | + } |
| 73 | +} |
| 74 | + |
| 75 | +/** |
| 76 | + * Your LRUCache object will be instantiated and called as such: |
| 77 | + * var obj = LRUCache(capacity) |
| 78 | + * var param_1 = obj.get(key) |
| 79 | + * obj.put(key,value) |
| 80 | + */ |
0 commit comments