Leetcode: Populating Next Right Pointers in Each Node II in C++

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

Solution: Modify from previous code
void connect(TreeLinkNode *root) {
         TreeLinkNode *pre = NULL;
        TreeLinkNode *cur = root;
        TreeLinkNode *lead = root;
        TreeLinkNode* left,*right;
        while(cur)
        {
            left = cur->left;
            right = cur->right;
           if(left)
            {
                if(pre)
                pre->next = left;
                pre = left;
            }
            if(right)
            {
               if(pre)
               pre->next = right;
               pre = right;
            }
            if(cur->next)
            cur = cur->next;
            else
            {
               //find first item in next line
                while(lead&&!lead->left&&!lead->right)
                lead = lead->next;
                if(!lead)
                break;
                if(lead->left)
                cur = lead->left;
                else
                cur = lead->right;
                lead = cur;
                pre = NULL;
            }
        }