Question

1) Recall that within theArrayBoundedStackthetopIndexvariable holds the index of theelementsarray where the current top of stack is stored. If a stack is empty, then itstopIndexvariableis:

a) -1

b) 0

c) 1

d) DEFCAP  

e) None of above

8) Evaluate the following postfix expression:  6  4 + 3  10  * 2 2 2 - +  * +

What is the highest number of elements on our stack at any one time?  

a) 2

b) 3

c) 4  

d) 5

e) None of above

Answer 1

1)  a) -1
when stack is empty, then top is -1

2)  d) 5
6 4 + 3 10 * 2 2 2 - + * +
--------------------------------
stack: []
push 6
stack: [6]
push 4
stack: [6 4]
pop, 6 and 4, push 6+4 = 10
stack: [10]
push 3
stack: [10 3]
push 10
stack: [10 3 10]
pop, 3 and 10, push 3*10 = 30
stack: [10 30]
push 2
stack: [10 30 2]
push 2
stack: [10 30 2 2]
push 2
stack: [10 30 2 2 2]
pop, 2 and 2, push 2-2 = 0
stack: [10 30 2 0]
pop, 2 and 0, push 2+0 = 2
stack: [10 30 2]
pop, 30 and 2, push 30*2 = 60
stack: [10 60]
pop, 10 and 60, push 10+60 = 70
stack: [70]

value of this expression is 70
and we can see that maximum size of stack is 5