CODE 25. Convert Sorted Array to Binary Search Tree

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

public TreeNode sortedArrayToBST(int[] num) {
	// Start typing your Java solution below
	// DO NOT write main() function
	if (num == null || num.length <= 0) {
		return null;
	}
	return dfs(num, 0, num.length - 1);
}

TreeNode dfs(int[] num, int min, int max) {
	TreeNode node = null;

	if (min <= max) {
		int mid = (max + min) / 2;
		node = new TreeNode(num[mid]);
		TreeNode left = dfs(num, min, mid - 1);
		TreeNode right = dfs(num, mid + 1, max);
		node.left = left;
		node.right = right;
	}
	return node;
}