Top and Bottom Elements of a Stack and Miscellaneous CS Concepts

Problem Statement

In the following postfix expression, what are the values of the top and bottom of the stack before the second '*' operation is performed? 632*/321*-+ Top: 1, Bottom: 6 Top: 2, Bottom: 6 Top: 3, Bottom: 6 Top: 6, Bottom: 6 You are given an array arr[], which contains N integers. A valid pair is any two indices i and j where i < j and a[i] - a[j] = j - i. Which of the following data structures is best suited to count the number of valid pairs efficiently? Stack Queue Hash Map Linked List An inversion in an array 'a' is a distinct pair of indices (i, j) where i < j and a[i] > a[j]. How many inversions are in a = {5, 7, 9, 2, 3, 12, 8, 4}? 12 13 14 15 What is the result of the SQL statement: SELECT ROUND(45.926, -2) FROM DUAL; 45.93 46 0 100 Which expression regarding MySQL Joins is not correct? INNER JOIN returns records with matching values in both tables LEFT JOIN returns all records from the left table and matched records from the right CROSS JOIN returns the Cartesian product