Leetcode 之Populating Next Right Pointers in Each Node II（51）

void connect(TreeLinkNode *root)
{
while (root)
{
//每一层循环时重新初始化
TreeLinkNode *prev = nullptr;
TreeLinkNode *next = nullptr;
//对于每一层
for (; root; root = root->next)
{
//每一层开始时，记录下一层的起始结点
if (!next)next = root->left ? root->left : root->right;

if (root->left)
{
//如果不是起始结点，则将prev与该左子结点相连接
if (prev)prev->next = root->left;
//如果是每层的起始结点，则将左子结点直接赋给prev
prev = root->left;
}
if (root->right)
{
if (prev)prev->next = root->right;
prev = root->right;
}
}
root = next;
}
}