convert-sorted-array-to-binary-search-tree

packagecom.ytx.array;

/**

 * convert-sorted-array-to-binary-search-tree

 *

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

 *

 *@authoryuantian xin

 *  把一个升序的有序数组转换成高度平衡的二叉搜索树

 * 

 *  平衡的二叉搜索树，即每棵子树的根节点都是二分查找的中间节点，

 *  使用二分法的递归得到每个中间节点即可。

 */

classTreeNode {

       

       intdata;

       

       TreeNodeleft;

       

       TreeNoderight;

       

       publicTreeNode(intdata) {

             this.data= data;

       }

       

}

publicclassConvert_sorted_array_to_binary_search_tree {

       

       publicTreeNode buildBinarySearchTree(int[]num , intstart,intend) {

             

             if(start > end)returnnull;

             

             intmid = (start + end + 1) / 2;

             

             TreeNode root = newTreeNode(num[mid]);

             

             root.left= buildBinarySearchTree(num,start,mid - 1);

             

             root.right= buildBinarySearchTree(num,mid + 1, end);

             

             returnroot;

             

       }

       

       public  TreeNode sortedArrayToBST(int[]num) {

             

             intlen = num.length;

             

       if(num== null || len <= 0 ) return null;

       

       return  buildBinarySearchTree(num, 0,len-1);

    }

}