Java实现多叉树和二叉树之间的互转

// 多叉树节点定义
public class Node {
   public int val;
   // 子节点是列表形式
   public List<Node> children;
   public Node(int _val) {
      val = _val;
   }
   public Node(int _val, List<Node> _children) {
      val = _val;
      children = _children;
   }
}
// 二叉树节点定义
public class TreeNode {
   int val;
   TreeNode left;
   TreeNode right;
   TreeNode(int x) {
      val = x;
   }
}

public TreeNode encode(Node root) {
   if (root == null) {
      return null;
   }
   TreeNode head = new TreeNode(root.val);
   head.left = en(root.children);
   return head;
}
private TreeNode en(List<Node> children) {
   TreeNode head = null;
   TreeNode cur = null;
   for (Node child : children) {
      TreeNode tNode = new TreeNode(child.val);
      if (head == null) {
         head = tNode;
      } else {
         cur.right = tNode;
      }
      cur = tNode;
      cur.left = en(child.children);
   }
   return head;
}

public Node decode(TreeNode root) {
   if (root == null) {
      return null;
   }
   return new Node(root.val, de(root.left));
}
public List<Node> de(TreeNode root) {
   List<Node> children = new ArrayList<>();
   while (root != null) {
      Node cur = new Node(root.val, de(root.left));
      children.add(cur);
      root = root.right;
   }
   return children;
}