[LeetCode] Convert Sorted Array to Binary Search Tree

问题：

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

分析：

简单的一道递归题。

代码：

class Solution {
public:
	TreeNode *sortedArrayToBST(const vector<int> &num, int start, int end) {
		if (start > end) return 0;
		if (start == end) return new TreeNode(num[start]);
		int mid = (start + end) / 2;
		TreeNode *root = new TreeNode(num[mid]);
		root->left = sortedArrayToBST(num, start, mid - 1);
		root->right = sortedArrayToBST(num, mid + 1, end);
		return root;
	}

	TreeNode *sortedArrayToBST(vector<int> &num) {
		int len = num.size();
		if (len == 0) return 0;
		if (len == 1) return (new TreeNode(num[0]));
		return sortedArrayToBST(num, 0, len - 1);
	}
};