/// <summary>
/// 递归遍历
/// </summary>
/// <param name="root"></param>
/// <param name="arr"></param>
private void inorderTraversal(TreeNode root, List <int> arr)
{
if (root == null)
{
return;
}
inorderTraversal(root.left, arr); // 增加节点 左侧
arr.Add(root.val); // 增加节点 自身
inorderTraversal(root.right, arr); // 增加节点 右侧
}
public List <int> inorder(TreeNode root, List <int> arr)
{
if (root == null)
{
return(arr);
}
inorder(root.left, arr);
arr.Add(root.val);
inorder(root.right, arr);
return(arr);
}
public override bool Test(System.Diagnostics.Stopwatch sw)
{
bool isSuccess = true;
int num = 0;
TreeNode node = new TreeNode();
Codec obj = new Codec();
string data = obj.serialize(node);
TreeNode des = obj.deserialize(data);
return(isSuccess);
}
public override bool Test(System.Diagnostics.Stopwatch sw)
{
bool isSuccess = true;
TreeNode treeRoot = TreeNode.CreateBST(new int[] { 7, 3, 15, 9, 20 });//??? { 7, 3, 15, null, null, 9, 20 }
BSTIterator bSTIterator = new BSTIterator(treeRoot);
System.Diagnostics.Debug.Assert(bSTIterator.next() == 3); // 返回 3
System.Diagnostics.Debug.Assert(bSTIterator.next() == 7); // 返回 7
System.Diagnostics.Debug.Assert(bSTIterator.hasNext() == true); // 返回 True
System.Diagnostics.Debug.Assert(bSTIterator.next() == 9); // 返回 9
System.Diagnostics.Debug.Assert(bSTIterator.hasNext() == true); // 返回 True
System.Diagnostics.Debug.Assert(bSTIterator.next() == 15); // 返回 15
System.Diagnostics.Debug.Assert(bSTIterator.hasNext() == true); // 返回 True
System.Diagnostics.Debug.Assert(bSTIterator.next() == 20); // 返回 20
System.Diagnostics.Debug.Assert(bSTIterator.hasNext() == false); // 返回 False
return(isSuccess);
}
public override bool Test(System.Diagnostics.Stopwatch sw)
{
bool isSuccess = true;
int checkresult;
int k;
TreeNode node;
node = TreeNode.Create(new string[] { "5", "3", "6", "2", "4", null, null, "1" });
k = 3;
checkresult = 3;
isSuccess &= KthSmallest(node, k) == checkresult;
node = TreeNode.Create(new string[] { "3", "1", "4", null, "2" });
k = 1;
checkresult = 1;
isSuccess &= KthSmallest(node, k) == checkresult;
System.Diagnostics.Debug.Assert(isSuccess);
return(isSuccess);
}
/// <summary>
/// 二叉搜索树中第K小的元素
/// 通过构造 BST 的中序遍历序列，则第 k-1 个元素就是第 k 小的元素。
///
/// Your runtime beats 98.95 % of csharp submissions
/// Your memory usage beats 7.37 % of csharp submissions
///
/// </summary>
/// <param name="root"></param>
/// <param name="k"></param>
/// <returns></returns>
public int KthSmallest_MySelf(TreeNode root, int k)
{
List <TreeNode> nodeList = new List <TreeNode>();
TreeNode.GetNodeList(root, nodeList);
return(nodeList[k - 1].val);
/*
* /// 自己最初的算法，效率很低。
* /// Your runtime beats 22.11 % of csharp submissions
* /// Your memory usage beats 5.27 % of csharp submissions(29.3 MB)
* List<int> nodeValues = new List<int>();
* foreach(TreeNode node in nodeList)
* {
* if(node != null)
* nodeValues.Add(node.val);
* }
* nodeValues.Sort();
* return nodeValues[k-1];
*/
}
// Encodes a tree to a single string.
public string serialize(TreeNode root)
{
return("");
}
/// 官方答案，其实和自己的一样。
public int KthSmallest(TreeNode root, int k)
{
List <int> nums = inorder(root, new List <int>());
return(nums[k - 1]);
}
public BSTIterator(TreeNode root)
{
idx = 0;
arr = new List <int>();
inorderTraversal(root, arr);
}
