95. 不同的二叉搜索树 II

src/com/gatsby/_95UniqueBinarySearchTreesII.java

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+package com.gatsby;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @ClassName: _95UniqueBinarySearchTreesII
+ * @Description:
+ * @author: Gatsby
+ * @date: 2022/8/4 9:51
+ */
+
+public class _95UniqueBinarySearchTreesII {
+
+
+    public List<TreeNode> generateTrees(int n) {
+
+        if (n == 0) return new ArrayList<>();
+        else return generateTrees(1, n);
+    }
+
+    public List<TreeNode> generateTrees(int start, int end) {
+        List<TreeNode> res = new ArrayList<>();
+
+        if (start > end) {
+            res.add(null);
+            return res;
+        }
+
+        for (int i = start; i <= end; ++i) {
+            List<TreeNode> left = generateTrees(start, i - 1);
+            List<TreeNode> right = generateTrees(i + 1, end);
+
+            for (TreeNode l : left) {
+                for (TreeNode r : right) {
+                    TreeNode node = new TreeNode(i);
+                    node.left = l;
+                    node.right = r;
+                    res.add(node);
+                }
+            }
+
+        }
+        return res;
+    }
+}
+
+