LeetCode 117:Populating Next Right Pointers in Each Node II

Follow up for problem "Populating Next Right Pointers in Each Node".

What if the given tree could be any binary tree? Would your previous solution still work?

Note:

• You may only use constant extra space.

For example,
Given the following binary tree,

         1
       /  
      2    3
     /     
    4   5    7

After calling your function, the tree should look like:

         1 -> NULL
       /  
      2 -> 3 -> NULL
     /     
    4-> 5 -> 7 -> NULL

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//二叉树进行层次遍历
//推断最底层的条件：假设当前訪问的层有任一节点存在子节点，说明当前层不是最底层。
class Solution{
public:
	TreeLinkNode* nextLeft;
	bool hasToTheEnd;
	void connect(TreeLinkNode *root)
	{
		if (!root)  return;

		hasToTheEnd = false;
		int level = 1;
		while (!hasToTheEnd)
		{
			hasToTheEnd= true;
			nextLeft= NULL;
			VisitLevel(root, level);
			++level;
		}
	}

	void VisitLevel(TreeLinkNode* node, int level)
	{
		if (level == 1)
		{
			if (nextLeft != NULL)
			{
				nextLeft->next = node;
			}
			nextLeft = node;

			if (node->left != NULL || node->right != NULL)
			{
				hasToTheEnd= false;
			}
		}

		if (node->left)	  VisitLevel(node->left, level - 1);
		if (node->right)  VisitLevel(node->right, level - 1);
	}
};