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ConvertSortedListtoBinarySearchTree.java

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/**

* Given a singly linked list where elements are sorted in ascending order,

* convert it to a height balanced BST.

*/

public class ConvertSortedListtoBinarySearchTree {

public TreeNode sortedListToBST(ListNode head) {

return sortedListToBST(head, null);

}

private TreeNode sortedListToBST(ListNode start, ListNode end) {

if (start == end) {

return null;

} else if (start.next == end) {

return new TreeNode(start.val);

} else {

ListNode fast = start, slow = start;

while (fast.next != end && fast.next.next != end) {

fast = fast.next.next;

slow = slow.next;

}

TreeNode left = sortedListToBST(start, slow);

TreeNode right = sortedListToBST(slow.next, end);

TreeNode root = new TreeNode(slow.val);

root.left = left;

root.right = right;

return root;

}

}

}