leetcode - 剑指 Offer 36. 二叉搜索树与双向链表

#include 
#include 
using namespace std;

typedef struct Node{
	int val;
	struct Node *left, *right;
}Node, *ListNode;

Node *pre, *head;

void dfs(Node *cur){
	if(!cur){
		return NULL;
	}
	dfs(cur->left);
	if(pre){
		pre->right = cur;
	}else{
		head = cur;
	}
	cur->left = pre;
	pre = cur;
	dfs(cur->right);
}

Node* treeToDoublyList(Node* root) {
	if(!root){
		return NULL;
	} 
	dfs(root);
	head->left = pre;
	pre->right = head;
	return head;       
}

int main(){
	Node *root, res; 
	res = treeToDoublyList(root);
	return 0;
}