Java solution 95

Author: gavinfish

java/_095UniqueBinarySearchTreesII.java

@@ -0,0 +1,36 @@
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Created by drfish on 27/05/2017.
+ */
+public class _095UniqueBinarySearchTreesII {
+    public List<TreeNode> generateTrees(int n) {
+        List<TreeNode> result = genTrees(1, n);
+        if (result.get(0) == null) {
+            return new ArrayList<>();
+        } else {
+            return result;
+        }
+    }
+
+    private List<TreeNode> genTrees(int start, int end) {
+        List<TreeNode> result = new ArrayList<>();
+        if (start > end) {
+            result.add(null);
+        }
+        for (int i = start; i <= end; i++) {
+            List<TreeNode> leftTrees = genTrees(start, i - 1);
+            List<TreeNode> rightTrees = genTrees(i + 1, end);
+            for (TreeNode leftTree : leftTrees) {
+                for (TreeNode rightTree : rightTrees) {
+                    TreeNode root = new TreeNode(i);
+                    root.left = leftTree;
+                    root.right = rightTree;
+                    result.add(root);
+                }
+            }
+        }
+        return result;
+    }
+}