代码

/*
// Definition for a Node.
class Node {public int val;public Node left;public Node right;public Node next;public Node() {}public Node(int _val) {val = _val;}public Node(int _val, Node _left, Node _right, Node _next) {val = _val;left = _left;right = _right;next = _next;}
};
*/class Solution {public Node connect(Node root) {if(root==null||root.left==null) return root;root.left.next=root.right;//连接左右子树if(root.next!=null)root.right.next=root.next.left;//连接隔壁节点的左子树connect(root.left);//dfsconnect(root.right);return root;}
}