Create 0095-unique-binary-search-trees-ii.kt

Author: a93a

kotlin/0095-unique-binary-search-trees-ii.kt

@@ -0,0 +1,28 @@
+class Solution {
+    fun generateTrees(n: Int): List<TreeNode?> {
+        val dp = HashMap<Pair<Int, Int>, List<TreeNode?>>()
+        
+        fun generate(l: Int, r: Int): List<TreeNode?> {
+            if (l == r) return arrayListOf(TreeNode(l))
+            if (l > r) return arrayListOf<TreeNode?>(null)
+            if (dp[l to r] != null) return dp[l to r]!!
+            
+            val res = ArrayList<TreeNode?>()
+            for (i in l..r) {
+                val left = generate(l, i - 1)
+                val right = generate(i + 1, r)
+                for (nodeLeft in left) {
+                    for (nodeRight in right) {
+                        val root = TreeNode(i, nodeLeft, nodeRight)
+                        res.add(root)
+                    }
+                }
+            }
+
+            dp[l to r] = res
+            return res
+        }
+
+        return generate(1, n)
+    }
+}