A program attempts to generate as many permutation as possible of the string “abcd” by pushing the character a,b,c,d in the same order onto a stack, but it may pop off the top character at any time. Which one of the following a strings CANNOT be generated using this program?

Let S be a stack of size n >= 1. Starting with the empty stack, suppose we push the first n natural numbers in sequence, and then perform n pop operations. Assume that Push and Pop operations take X seconds each, and Y seconds elapse between the end of one such stack operation and the start of the next operation. For m >= 1, define the stack-life of m as the time elapsed from the end of Push(m) to the start of the pop operation that removes m from S. The average stack-life of an element of this stack is

Compute the post fix equivalent of the following expression. 3 * log(x+1) - a/2

What value would the following function return for the input x = 95?

 function fun (x:integer):integer; 
   Begin 
      If x > 100 then fun : x – 10 
      Else fun : fun(fun (x + 11)) 
   End;