Q:
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted array: [-10,-3,0,5,9], One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST: 0 / \ -3 9 / / -10 5
A:
/*** Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: TreeNode* sortedArrayToBST(vector<int>& nums) { return helper(nums, 0, nums.size()); } private: TreeNode* helper(vector<int>& nums, int a, int b) // (a, b] { if(a>=b) return NULL; int mid = (a+b)/2; TreeNode *root = new TreeNode(nums[mid]); root->left = helper(nums,a, mid); root->right = helper(nums, mid+1, b); return root; } };
Mistakes:
1: 啊啊啊, damn it.
b 可以是虚的,也可以是实的。 如果用虚的,会比较容易写。
No comments:
Post a Comment