LeetCode: Populating Next Right Pointers in Each Node

class Solution { public: Node* connect(Node* root) { queue<Node*> Q; Node* cur; if(root) Q.push(root); while(!Q.empty()) { int sz = Q.size(); Node* pre = NULL; for(int i=0; i<sz; i++) { cur = Q.front(); Q.pop(); if(cur->left) Q.push(cur->left); if(cur->right) Q.push(cur->right); if(pre) pre->next = cur; pre = cur; } } return root; } };