LeetCode 114: Flatten Binary Tree to Linked List

原创于 2013-09-03 13:13:19 发布 · 404 阅读

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本文介绍了一种将二叉树结构通过特定算法展平为链表的方法。通过递归方式处理二叉树的左右子节点，最终使得每个节点的左指针为空，而右指针指向下一个节点，形成一个链表。该方法适用于计算机科学中的数据结构转换场景。

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Difficulty: 3

Frequency: 3

Problem:

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

The flattened tree should look like:

Solution:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void flatten(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        flattenRecursive(root);
    }
    TreeNode * flattenRecursive(TreeNode * root)
    {
        if (root==NULL)
            return NULL;
        
        TreeNode * left = flattenRecursive(root->left);
        TreeNode * right = flattenRecursive(root->right);
        
        TreeNode * traverse = root;
        traverse->right = left;
        while(traverse->right!=NULL)
        {
            traverse = traverse->right;
        }
        traverse->right = right;
        root->left = NULL;// This one is important.
        return root;
    }
};

Notes: