1+ class LFUCache (private val capacity : Int ) {
2+ 3+ private data class Item (var value : Int , var frequency : Int )
4+ 5+ private var minFrequency = 0
6+ private val items = hashMapOf<Int , Item >()
7+ private val frequencySets = hashMapOf<Int , MutableSet <Int >>()
8+ 9+ private fun getItem (key : Int ): Item ? {
10+ val item = items.get(key) ? : return null
11+ val frequencySet = frequencySets.get(item.frequency)!!
12+ 13+ frequencySet.remove(key)
14+ 15+ if (minFrequency == item.frequency && frequencySet.isEmpty()) {
16+ minFrequency + = 1
17+ }
18+ 19+ item.frequency + = 1
20+ frequencySets.getOrPut(item.frequency) { mutableSetOf () }.add(key)
21+ 22+ return item
23+ }
24+ 25+ 26+ fun get (key : Int ): Int {
27+ return getItem(key)?.value ? : - 1
28+ }
29+ 30+ fun put (key : Int , value : Int ) {
31+ if (capacity == 0 ) return
32+ 33+ val item = getItem(key)
34+ 35+ if (item != null ) {
36+ item.value = value
37+ } else {
38+ val newItem = Item (value, 1 )
39+ 40+ if (items.size == capacity) {
41+ val frequencySet = frequencySets.get(minFrequency)!!
42+ val keyToRemove = frequencySet.first()
43+ 44+ frequencySet.remove(keyToRemove)
45+ items.remove(keyToRemove)
46+ }
47+ 48+ minFrequency = 1
49+ items[key] = newItem
50+ frequencySets.getOrPut(1 ) { mutableSetOf () }.add(key)
51+ }
52+ }
53+ 54+ }
55+ 56+ /* *
57+ * Your LFUCache object will be instantiated and called as such:
58+ * var obj = LFUCache(capacity)
59+ * var param_1 = obj.get(key)
60+ * obj.put(key,value)
61+ */
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