-find the right most element in tree if postorder and inorder is given -how many binary can made with 3 nodes - 5 -binary search questn -optional keyword in java 8 , null and absent value -which language in not JVM , groovy -time complexity to find min element in max heap. O(n) -which sort is not react same every time , quicksort -algorithm for the count-distinct problem, approximating the number of distinct elements in a multiset. - HyperLogLog