[LeetCode] Populating Next Right Pointers in Each Node II

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

問題解決の考え方:
Populating Next Right Pointers in Each Nodeと似ていますが、ここの二叉木は任意の二叉木です.階層の最初の子供ノードを持つツリーノードを記録する必要があります.状況別に議論し,状況の分岐はコードに注釈した.

/**
 * Definition for binary tree with next pointer.
 * struct TreeLinkNode {
 *  int val;
 *  TreeLinkNode *left, *right, *next;
 *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
 * };
 */
class Solution {
public:
    void connect(TreeLinkNode *root) {
        if(root==NULL){
            return;
        }
        TreeLinkNode* upLayerFirstNode = root;
        TreeLinkNode* upLayerNode = root;
        TreeLinkNode* node = root->left==NULL ? root->right : root->left;
        while(node!=NULL){
            bool findUpLayerFirstNode = false;
            while(upLayerNode!=NULL){
                if(!findUpLayerFirstNode && (node->left!=NULL || node->right!=NULL)){
                    upLayerFirstNode = node;
                    findUpLayerFirstNode = true;
                }
                if(upLayerNode->left == node){  //               
                    if(upLayerNode->right!=NULL){
                        node->next = upLayerNode->right;
                        node = node->next;
                        upLayerNode = upLayerNode->next;
                    }else{
                        upLayerNode = upLayerNode->next;
                    }
                }else if(upLayerNode->right == node){ //               
                    upLayerNode = upLayerNode->next;
                }else if(upLayerNode->left!=NULL){  //                  ，            
                    node->next = upLayerNode->left;
                    node = node->next;
                }else if(upLayerNode->right!=NULL){ //            ，        ，            
                    node->next = upLayerNode->right;
                    node = node->next;
                    upLayerNode = upLayerNode->next;
                }else{                              //           
                    upLayerNode = upLayerNode->next;
                }
                if(!findUpLayerFirstNode && (node->left!=NULL || node->right!=NULL)){   //           ，         next   
                    upLayerFirstNode = node;
                    findUpLayerFirstNode = true;
                }
            }
            if(findUpLayerFirstNode){
                upLayerNode=upLayerFirstNode;
                node = upLayerFirstNode->left==NULL ? upLayerFirstNode->right : upLayerFirstNode->left;
            }else{
                node = NULL;
            }
        }
    }
};