the second interview question: design a malloc function that guarantees that the address it returns is a multiplicand of 64. after that design a free function that takes such address and frees all allocated memory. both the functions can be implemented using the built in malloc and free, using a little tweek.

q2) delete a node in a linked list given a pointer to the node we want to delete (can be done in O(1)).

q3) given an array that contains numbers that appear only once or twice, return all the number that appear twice (non trivial solution for O(N) time and O(1) space).