Tree transfer list

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Title Description

A similar data structure node TreeNode, val contains attributes and pointers to other nodes. It can be used to represent a binary search tree (which left pointer represents the left son, right for right pointer son). Please write a method, the binary search tree into a linked list data structure to achieve a binary search tree with TreeNode, linked list data structure with ListNode achieve.

Given a binary search tree root pointer root, converted into a return to head pointer list.

 

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
class Converter {
public:
    ListNode* head;
    ListNode* cur;
    ListNode* treeToList(TreeNode* root) 
    {
        // write code here
        head = new ListNode(0);
        cur = head;
        fun(root);
        ListNode *temp = head;
        head = head ->next;
        delete temp;
        return head;
    }
    
    void fun(TreeNode* root)
    {
        if(!root)
            return;
        fun(root ->left);
        cur ->next = new ListNode(root -> val);
        cur = cur ->next;
        fun(root ->right);
    }
};