LeetCode——Populating Next Right Pointers in Each Node

最新推荐文章于 2025-12-03 23:35:37 发布

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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。文章提供了一种仅使用常数额外空间的解决方案，并给出了具体的实现代码。

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

» Solve this problem

根据题意可知，该树为满二叉树。

所以left->next = right, right->next = father->next->left

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (root) {
            if (root->left) {
                root->left->next = root->right;
            }
            if (root->right) {
                root->right->next = root->next ? root->next->left : NULL;
            }
            connect(root->left);
            connect(root->right);
        }
    }
};