Create 1993-operations-on-tree.kt

Author: a93a

Diff for: kotlin/1993-operations-on-tree.kt

@@ -0,0 +1,53 @@
+class LockingTree(val parent: IntArray) {
+    val locked = IntArray (parent.size) { -1 }
+    val child = HashMap<Int, MutableList<Int>>()
+
+    init {
+        for (i in 1 until parent.size) {
+            child[parent[i]] = child.getOrDefault(parent[i], mutableListOf<Int>()).apply { add(i) }
+        }
+    }
+
+    fun lock(num: Int, user: Int): Boolean {
+        if (locked[num] != -1) 
+            return false
+        locked[num] = user
+        return true
+    }
+
+    fun unlock(num: Int, user: Int): Boolean {
+        if (locked[num] != user)
+            return false
+        locked[num] = -1
+        return true
+    }
+
+    fun upgrade(num: Int, user: Int): Boolean {
+        var i = num
+        while (i != -1) {
+            if (locked[i] != -1)
+                return false
+            i = parent[i]
+        }
+
+        var lockedCount = 0
+        var q = LinkedList<Int>()
+        q.add(num)
+        while (q.isNotEmpty()) {
+            var n = q.removeLast()
+            if (locked[n] != -1) {
+                locked[n] = -1
+                lockedCount++
+            }
+            child[n]?.forEach {
+                q.addFirst(it)
+            }
+        }
+
+        if (lockedCount > 0)
+            locked[num] = user
+        
+        return lockedCount > 0
+    }
+
+}