1. Which of the following is not a valid postfix expression? 5 4 + 6 5 4 + - 4 +
ID: 3805083 • Letter: 1
Question
1. Which of the following is not a valid postfix expression?
5 4 +
6 5 4 + -
4 + 5
8 2 + 2 /
all of the above are valid postfix expressions
2.
What is the result of evaluating the following postfix expression: 4 8 + 2 *
40
24
64
20
none of the above are correct
3.
What exception is thrown if the pop method is called on an empty stack?
EmptyStackException
NoSuchElementException
ArrayOutOfBoundsException
EmptyCollectionException
none of the above
4.
Which of the following methods removes an element from a queue?
enqueue
dequeue
first
pop
push
5.
Which of the following methods inserts an element into a stack data structure?
enqueue
dequeue
push
pop
peek
6.
A queue is helpful in implementing a __________________ sort.
insertion
selection
quick
radix
merge
5 4 +
6 5 4 + -
4 + 5
8 2 + 2 /
all of the above are valid postfix expressions
2.
What is the result of evaluating the following postfix expression: 4 8 + 2 *
40
24
64
20
none of the above are correct
Explanation / Answer
1) (c) 4+ 5 [because its an Infix expression]
2) 4 8 + 2 * . => 12 *2 = 24
3) EmptyStackException
4) dequeue removes element from queue . and enqueue adds elements into queue
5) push does the insertion and pop does the removal
6) We can say selection sort . Priority queue helps in implementing Heap Sort
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