LeetCode[Tree]: Populating Next Right Pointers in Each Node II

chfe910

于 2015-02-03 16:27:24 发布

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分类专栏： LeetCode LeetCode 文章标签： LeetCode Tree Algorithm C++ connect

本文链接：https://blog.youkuaiyun.com/chfe007/article/details/43451447

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针对Populating Next Right Pointers in Each Node问题，探讨了当输入为任意二叉树时解决方案的有效性，并提出了一种仅使用常数额外空间的方法。通过遍历每层节点并建立相邻节点间的连接，确保每个节点的next指针指向其右侧的下一个节点。同时，作者分享了自己的C++实现代码并指出其时间性能有待改进。

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Follow up for problem “Populating Next Right Pointers in Each Node”.
What if the given tree could be any binary tree? Would your previous solution still work?
Note:

You may only use constant extra space.

For example,
Given the following binary tree,

After calling your function, the tree should look like:

我的C++代码实现如下：

class Solution {
public:
    void connect(TreeLinkNode *root) {
        for (TreeLinkNode *levelFirstNode = root; levelFirstNode != nullptr; levelFirstNode = getNext(levelFirstNode)) {
            for (TreeLinkNode *curNode = levelFirstNode; curNode != nullptr; curNode = curNode->next) {
                if (curNode->left) curNode->left->next = curNode->right ? curNode->right : getNext(curNode->next);
                if (curNode->right) curNode->right->next = getNext(curNode->next);
            }
        }
    }

private:
    TreeLinkNode *getNext(TreeLinkNode *node) {
        while (node) {
            if (node->left) return node->left;
            if (node->right) return node->right;
            node = node->next;
        }

        return nullptr;
    }
};