refactor 95

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_95.java

@@ -5,7 +5,10 @@
 import java.util.ArrayList;
 import java.util.List;
 
-/**Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1...n.
+/**
+ * 95. Unique Binary Search Trees II
+ *
+ * Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1...n.
 
  For example,
  Given n = 3, your program should return all 5 unique BST's shown below.
@@ -17,37 +20,39 @@
  2     1         2                 3*/
 public class _95 {
 
-	public List<TreeNode> generateTrees_pure_recursion(int n) {
-		List<TreeNode> result = new ArrayList<TreeNode>();
-		if (n == 0) {
-			return result;
+	public static class Solution1 {
+		public List<TreeNode> generateTrees(int n) {
+			List<TreeNode> result = new ArrayList();
+			if (n == 0) {
+				return result;
+			}
+			return generateTrees(1, n);
 		}
-		return generateTrees(1, n);
-	}
 
-	private List<TreeNode> generateTrees(int start, int end) {
-		List<TreeNode> result = new ArrayList<TreeNode>();
-		if (start > end) {
-			result.add(null);
-			return result;
-		}
-		if (start == end) {
-			result.add(new TreeNode(start));
-			return result;
-		}
+		private List<TreeNode> generateTrees(int start, int end) {
+			List<TreeNode> result = new ArrayList();
+			if (start > end) {
+				result.add(null);
+				return result;
+			}
+			if (start == end) {
+				result.add(new TreeNode(start));
+				return result;
+			}
 
-		for (int i = start; i <= end; i++) {
-			List<TreeNode> leftList = generateTrees(start, i - 1);
-			List<TreeNode> rightList = generateTrees(i + 1, end);
-			for (TreeNode left : leftList) {
-				for (TreeNode right : rightList) {
-					TreeNode root = new TreeNode(i);
-					root.left = left;
-					root.right = right;
-					result.add(root);
+			for (int i = start; i <= end; i++) {
+				List<TreeNode> leftList = generateTrees(start, i - 1);
+				List<TreeNode> rightList = generateTrees(i + 1, end);
+				for (TreeNode left : leftList) {
+					for (TreeNode right : rightList) {
+						TreeNode root = new TreeNode(i);
+						root.left = left;
+						root.right = right;
+						result.add(root);
+					}
 				}
 			}
+			return result;
 		}
-		return result;
 	}
 }