[LeetCode]Flatten Binary Tree to Linked List

最新推荐文章于 2022-07-27 15:08:45 发布

原创最新推荐文章于 2022-07-27 15:08:45 发布 · 1.6k 阅读

0 ·

CC 4.0 BY-SA版权

LeetCode 专栏收录该内容

152 篇文章

订阅专栏

本文详细介绍了如何使用递归和迭代两种方法来实现二叉树的扁平化操作，包括具体步骤、代码实现以及性能对比。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
class Solution {
	//cue: looks like preorder 
public:
	TreeNode * ReLink(TreeNode *root)
	{
		if(!root || (!root->left && !root->right))
			return root;
		TreeNode* left = root->left;
		TreeNode* right = root->right;
		root->left = NULL;
		if(left)
		{
			root->right = left;
			root = ReLink(left);
		}
		if(right)
		{
			root->right = right;
			root = ReLink(right);
		}
		return root;
	}
    void flatten(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
		ReLink(root);
    }
};

second time

/**
 * 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 flattenUtil(TreeNode* root, TreeNode*& prev)
    {
        if(root == NULL) return;
        if(prev != NULL) prev->right = root;
        prev = root;
        TreeNode* right = root->right;        
        flattenUtil(root->left, prev);
        root->left = NULL;
        flattenUtil(right, prev);
    }
    void flatten(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        TreeNode* prev = NULL;
        flattenUtil(root, prev);
    }
};