LeetCode 數組轉二叉樹 C#

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把LeetCode二叉樹題目的測試數組，轉換成二叉樹

class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(int x) { val = x; }
}
class Tree {
public static TreeNode CreateNode(int? val) {
if (val == null) return null;
return new TreeNode((int)val);
}
public static TreeNode CreateTree(int?[] arr) {
if (arr.Length <= 0 || arr[0] == null) {
return null;
}
TreeNode root = Tree.CreateNode(arr[0]);
Queue<TreeNode> queue = new Queue<TreeNode>();
queue.Enqueue(root);
int index = 1;
while (queue.Count > 0) {
TreeNode node = queue.Dequeue();
if (index < arr.Length) {
node.left = Tree.CreateNode(arr[index++]);
queue.Enqueue(node.left);
}
if (index < arr.Length) {
node.right = Tree.CreateNode(arr[index++]);
queue.Enqueue(node.right);
}
}
return root;
}
public static void Walk(TreeNode node, Action<TreeNode> func, TreeWalkType type) {
if (node != null) {
if (type == TreeWalkType.Pre) func(node);
Walk(node.left, func, type);
if (type == TreeWalkType.In) func(node);
Walk(node.right, func, type);
if (type == TreeWalkType.Post) func(node);
}
}
public static void InOrderTreeWalk(TreeNode root, Action<TreeNode> func) {
if (root == null) {
return;
}
Stack<TreeNode> stack = new Stack<TreeNode>();
TreeNode current = root;
while (current != null) {
stack.Push(current);
current = current.left;
}
while (stack.Count != 0) {
current = stack.Pop();
func(current);             //func
TreeNode node = current.right;
while (node != null) {
stack.Push(node);
node = node.left;
}
}
}
}
enum TreeWalkType {
Pre,
In,
Post
}

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LeetCode 數組轉二叉樹 C#