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/**

* Convert sorted array to binary search tree

//Idea: this is to test your ability for recursive

//Find the middle index of the array, that will be the rot of the array

//recursively devided the array into half by half and continuously find the root for subtree

public static TreeNode sortedArrayToBST(int[] num, int start, int end) {

if (num.length == 0) { //If empty array, then empty tree

return null;

}

int startIndex = (start == null) ? 0 : start;

int endIndex = (end == null) ? (num.length -1) : end; //end index is last index of the array

int mid = (startIndex + endIndex) / 2;

//Create treenode, left and right

TreeNode root = new TreeNode(num[mid]);

root.left = sortedArrayToBST(num, startIndex, mid -1);

root.right = sortedArrayToBST(num, mid, endIndex);

return root;

}