【leetcode】【单链表】【109】Convert Sorted List to Binary Search Tree

#include<iostream>
using namespace std;

struct ListNode {
    int val;
    ListNode *next;     
	ListNode(int x) : val(x), next(NULL) {}
 };
struct TreeNode {
	int val;
    TreeNode *left;
	TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
	TreeNode* inorderTraversal(ListNode* &head, int start, int end){ //中序遍历
		if (start > end)
			return NULL;
		int mid = start + (end - start) / 2;
		TreeNode* left = inorderTraversal(head, start, mid - 1);
		TreeNode* root = new TreeNode(head->val);
		root->left = left;
		head = head->next;
		root->right = inorderTraversal(head, mid + 1, end);
		return root;
	}
	TreeNode* sortedListToBST(ListNode* head) {
		int numOfNodes = 0;
		ListNode* cur = head;
		while (cur){
			++numOfNodes;
			cur = cur->next;
		}
		return inorderTraversal(head, 0, numOfNodes - 1);
	}
	ListNode* createList(ListNode* head){
		int numOfNode;
		int value;
		cout << "please input number of listNode:";
		cin >> numOfNode;
		cin >> value;
		head = new ListNode(value);
		ListNode* cur = head;
		for (int i = 1; i < numOfNode; ++i){
			cin >> value;
			ListNode* temp = new ListNode(value);
			cur->next = temp;
			cur = temp;
		}
		//cur->next = head;
		return head;
	}
	void printNode(ListNode* head){
		ListNode* cur = head;
		while (cur){
			cout << cur->val << " ";
			cur = cur->next;
		}
		cout << endl;
	}
};

void inorder(TreeNode* node){
	if (node){
		inorder(node->left);
		cout << node->val << " ";
		inorder(node->right);
	}
}

int main(){
	ListNode* head = NULL;
	Solution lst;
	head = lst.createList(head);
	lst.printNode(head);

	TreeNode* root = lst.sortedListToBST(head);
	if(root){
		inorder(root);
		cout << endl;
	}else{
		cout << "empty tree" << endl;
	}

	system("pause");
	return 0;
}