Populating Next Right Pointers in Each Node

class Solution {
public:
    void connect(TreeLinkNode *root) {
       
        if(!root) return;
        if(root->left&&root->right)     root->left->next=root->right;
        if(root->next&&root->left)     root->right->next=root->next->left;   //判断root->right是否为空;
        connect(root->left);
        connect(root->right);
    }
    
};