#填充每个节点指向最右节点的next指针#基于vector

/**
 * 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 == nullptr) return;

        vector<TreeLinkNode*> arr;
        arr.insert(arr.begin(), root);

        while (!arr.empty()) {
            int n = arr.size();
            for (int i = 0; i < n - 1; i++) {
                arr[i]->next = arr[i + 1];
            }
            arr[n - 1]->next = nullptr;
            for (int i = 0; i < n; i++) {
                TreeLinkNode* node = *arr.begin();
                arr.erase(arr.begin());
                if (node->left) arr.push_back(node->left);
                if (node->right) arr.push_back(node->right);
            }
        }
    }
};