116. Populating Next Right Pointers in Each Node

题目链接

https://leetcode.com/problems/populating-next-right-pointers-in-each-node/

代码

class Solution {
public:
    Node* connect(Node* root) {
        if (root == NULL) {
            return NULL;
        }
        queue que;
        que.push(root);
        que.push(NULL);
        Node* pre = NULL, *cur;
        while (true) {
            cur = que.front();
            que.pop();
            
            if (pre != NULL) {
                pre->next = cur;
            }
            pre = cur;
            
            if (cur == NULL) {
                if (que.empty()) {
                    break;
                } else {
                    pre = NULL;
                    que.push(NULL);
                }
            } else {
                if (cur->left != NULL) {
                    que.push(cur->left);
                }
                if (cur->right != NULL) {
                    que.push(cur->right);
                }
            }
        }
        return root;
    }
};