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)     {    if(!root)return;    TreeLinkNode *pNode=root;    while(pNode)    {    TreeLinkNode *nextLevel=0;    TreeLinkNode *prev=0;    for(;pNode;pNode=pNode->next)    {    if(!nextLevel)nextLevel=(pNode->left?pNode->left:pNode->right);    if(pNode->left)    {    if(prev)    {    prev->next=pNode->left;    }    prev=pNode->left;    }    if(pNode->right)    {    if(prev)    {    prev->next=pNode->right;    }    prev=pNode->right;    }    }    pNode=nextLevel;    }                }};