Populating Next Right Pointers in Each Node II

/**
 * 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) 
    {
        vector<TreeLinkNode*> list;
        if(root==NULL) return;
        
        list.push_back(root);
        while(list.size()>0)
        {
            vector<TreeLinkNode*> children;
            for(int i=0;i<list.size();i++)
            {
                if(list[i]->left!=NULL) 
                {
                    children.push_back(list[i]->left);
                    if(children.size()>1) children[children.size()-2]->next=children[children.size()-1];
                }
                if(list[i]->right!=NULL) 
                {
                    children.push_back(list[i]->right);
                    if(children.size()>1) children[children.size()-2]->next=children[children.size()-1];
                }
            }
            list=children;
        }
    }
};