题目:
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
源代码:
public class Solution {
public TreeNode sortedArrayToBST(int[] num) {
if(num == null || num.length <= 0){
return null;
}
return sortedArrayToBST(num, 0, num.length - 1);
}
private TreeNode sortedArrayToBST(int[] num, int begin, int end) {
if(begin == end){ //==
return new TreeNode(num[begin]);
}else if(begin == end - 1){
TreeNode n = new TreeNode(num[begin]);
n.right = sortedArrayToBST(num, end, end);
return n;
}
int mid = begin + (end - begin) / 2;
TreeNode root = new TreeNode(num[mid]);
root.left = sortedArrayToBST(num, begin, mid - 1);
root.right = sortedArrayToBST(num, mid + 1, end);
return root;
}
}