2022-06-01 update: added "Unique Binary Search Trees II"

Author: fartem

src/main/java/com/smlnskgmail/jaman/leetcodejava/medium/UniqueBinarySearchTreesII.java

@@ -0,0 +1,42 @@
+package com.smlnskgmail.jaman.leetcodejava.medium;
+
+import com.smlnskgmail.jaman.leetcodejava.support.TreeNode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+// https://leetcode.com/problems/unique-binary-search-trees-ii/
+public class UniqueBinarySearchTreesII {
+
+    private final int input;
+
+    public UniqueBinarySearchTreesII(int input) {
+        this.input = input;
+    }
+
+    public List<TreeNode> solution() {
+        return generate(1, input);
+    }
+
+    private List<TreeNode> generate(int i, int j) {
+        List<TreeNode> nodes = new ArrayList<>();
+        if (i > j) {
+            nodes.add(null);
+        } else {
+            for (int mid = i; mid <= j; mid++) {
+                List<TreeNode> left = generate(i, mid - 1);
+                List<TreeNode> right = generate(mid + 1, j);
+                for (TreeNode l : left) {
+                    for (TreeNode r : right) {
+                        TreeNode node = new TreeNode(mid);
+                        node.left = l;
+                        node.right = r;
+                        nodes.add(node);
+                    }
+                }
+            }
+        }
+        return nodes;
+    }
+
+}

src/test/java/com/smlnskgmail/jaman/leetcodejava/medium/UniqueBinarySearchTreesIITest.java

@@ -0,0 +1,65 @@
+package com.smlnskgmail.jaman.leetcodejava.medium;
+
+import com.smlnskgmail.jaman.leetcodejava.support.TreeNode;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class UniqueBinarySearchTreesIITest {
+
+    @Test
+    public void defaultTest() {
+        List<TreeNode> correct = List.of(
+                new TreeNode(
+                        1,
+                        null,
+                        new TreeNode(
+                                2,
+                                null,
+                                new TreeNode(3)
+                        )
+                ),
+                new TreeNode(
+                        1,
+                        null,
+                        new TreeNode(
+                                3,
+                                new TreeNode(2),
+                                null
+                        )
+                ),
+                new TreeNode(
+                        2,
+                        new TreeNode(1),
+                        new TreeNode(3)
+                ),
+                new TreeNode(
+                        3,
+                        new TreeNode(
+                                1,
+                                null,
+                                new TreeNode(2)
+                        ),
+                        null
+                ),
+                new TreeNode(
+                        3,
+                        new TreeNode(
+                                2,
+                                new TreeNode(1),
+                                null
+                        ),
+                        null
+                )
+        );
+        List<TreeNode> solution = new UniqueBinarySearchTreesII(3).solution();
+        assertEquals(correct.size(), solution.size());
+        for (int i = 0; i < correct.size(); i++) {
+            assertTrue(TreeNode.areEqual(correct.get(i), solution.get(i)));
+        }
+    }
+
+}