116. Populating Next Right Pointers in Each Node

最新推荐文章于 2022-04-05 16:12:16 发布

原创最新推荐文章于 2022-04-05 16:12:16 发布 · 144 阅读

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本文介绍了一种在完美二叉树中填充每个节点的next指针的方法，使得每个节点指向其右侧相邻节点。提供了两种解决方案，一种使用递归实现，另一种采用迭代方式，同时确保了额外空间复杂度为常数。

Given a binary tree

    struct TreeLinkNode {
      TreeLinkNode *left;
      TreeLinkNode *right;
      TreeLinkNode *next;
    }

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

Initially, all next pointers are set to NULL.

Note:

You may only use constant extra space.
You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).

For example,
Given the following perfect binary tree,

After calling your function, the tree should look like:

         1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \  / \
    4->5->6->7 -> NULL

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

class Solution {
public:
    void connect(TreeLinkNode *root) {
        TreeLinkNode* pre = root;
        TreeLinkNode* cur = NULL;
        while (pre) {
            cur = pre;
            while (cur && cur -> left) { 
                cur -> left -> next = cur -> right;
                if (cur -> next)
                    cur -> right -> next = cur -> next -> left;
                cur = cur -> next;
            }
            pre = pre -> left;
        }
    } 
};