题解 | 二叉搜索树与双向链表

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
private:
	TreeNode* first = nullptr;
	TreeNode* pre = nullptr;
	void midTrace(TreeNode* root){
		if(root == nullptr) return ;
		midTrace(root->left);
		if(first == nullptr){
			first = root;
			pre = root;
		}
		else{
			root->left = pre;
			pre -> right = root;
			pre = root;
		}
		midTrace(root->right);
	}
public:
    TreeNode* Convert(TreeNode* pRootOfTree) {
        midTrace(pRootOfTree);
		return first;
    }
};