# Definition for binary tree with next pointer.
# class TreeLinkNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#         self.next = None

class Solution:
    # @param root, a tree link node
    # @return nothing
    def connect(self, root):
        if root and root.left and root.right:
            root.left.next = root.right
            root.right.next = root.next and root.next.left
            return self.connect(root.left) or self.connect(root.right)