Leetcode#116 Populating Next Right Pointers in Each Node

 1 void connect(TreeLinkNode *root) {
 2   queue<TreeLinkNode *> layer;
 3 
 4   layer.push(root);
 5   while (!layer.empty()) {
 6     queue<TreeLinkNode *> nextLayer;
 7     TreeLinkNode *prev = NULL;
 8 
 9     while (!layer.empty()) {
10       TreeLinkNode *front = layer.front();
11       layer.pop();
12       if (!front)
13         continue;
14       if (prev)
15         prev->next = front;
16       prev = front;
17       nextLayer.push(front->left);
18       nextLayer.push(front->right);
19     }
20     layer = nextLayer;
21   }
22 }