Given Set = {12, 34, 22, 43, 13, 45, 55, 94, 99, 23} with 45 as the root
now make 2 sets ---------→ values less than root node elements ==> {12 , 34, 22 , 43, 13, 23}
---------→ values greater than root node ==> { 55, 94, 99}
As we get size as 6 (values less than 45) and 3 (values greater than 45)
Formula to find number of possible binary search trees = (2n)!
-------------------------
(n)! * (n+1)!
for n = 6 ===> (12! / (6! * 7!) ) ==> 132
for n = 3 ===> (6! / (3! * 4!) ) ==> 5
final answer will be 132 * 5 ==> 660