import java.util.ArrayList;

import java.util.List;

/**

* created by zl on 2019/4/28 13:03

*/

public class medium_95_UniqueBinarySearchTreesII

{

private List<TreeNode> generateNodeList(int si, int ei)

{

List<TreeNode> res = new ArrayList<>();

if (si > ei)

{

res.add(null);

return res;

}

if (si == ei)

{

res.add(new TreeNode(si));

return res;

}

for (int i = si; i <= ei; i++)

{

List<TreeNode> leftSubTrees = generateNodeList(si, i - 1);

List<TreeNode> rightSubTrees = generateNodeList(i + 1, ei);

for (TreeNode left : leftSubTrees)

{

for (TreeNode right : rightSubTrees)

{

TreeNode node = new TreeNode(i);

node.left = left;

node.right = right;

res.add(node);

}

}

}

return res;

}

public static void main(String[] args) {

medium_95_UniqueBinarySearchTreesII uniqueBinarySearchTreesII = new medium_95_UniqueBinarySearchTreesII();

List<TreeNode> res = new ArrayList<>();

res = uniqueBinarySearchTreesII.generateNodeList(1,4);

}

}