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ConvertSortedArraytoBinarySearchTree.h
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52 lines (42 loc) · 1.25 KB
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/**************************************
* Author : luoshikai
* Version : 1.0
* Date : 2013-11-05
* Email : luoshikai@gmail.com
*************************************/
/**************************************
* Given an array where elements are sorted in ascending order, convert it to a
* height balanced BST.
*************************************/
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode *sortedArrayToBST(vector<int> &num)
{
TreeNode *head = NULL;
if (num.empty()) return head;
sortedArrayToBSTRe(num, head, 0, num.size());
return head;
}
void sortedArrayToBSTRe(vector<int> &num, TreeNode *&node, int start, int length)
{
int mid = start + length / 2;
if (length <= 0 || start >= num.size())
{
node = NULL;
return;
}
node = new TreeNode(num[mid]);
sortedArrayToBSTRe(num, node->left, start, mid-start);
sortedArrayToBSTRe(num, node->right, mid+1, length-(mid-start)-1);
return;
}
};