代码随想录 Leetcode116/117.填充每个节点的下一个右侧节点指针（II)

题目：

代码(首刷自解 2024年1月24日）：

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* left;
    Node* right;
    Node* next;

    Node() : val(0), left(NULL), right(NULL), next(NULL) {}

    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}

    Node(int _val, Node* _left, Node* _right, Node* _next)
        : val(_val), left(_left), right(_right), next(_next) {}
};
*/

class Solution {
public:
    Node* connect(Node* root) {
        if(root == nullptr) return root;
        queue<Node*> que;
        Node* cur = root;
        que.push(cur);
        int size = 0;
        while (!que.empty()) {
            size = que.size();
            while (size--) {
                Node* node = que.front();
                que.pop();
                if (size == 0) node->next = nullptr;
                else node->next = que.front();
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
        }
        return root;
    }
};