Question discussion

The integers 1, 2, 3, 4 are pushed onto an initially empty stack in this order, and pops may be interleaved with the pushes at any time. Wh…

1771Medium DSSSB TGT Computer Science 0 replies 1 views

The integers 1, 2, 3, 4 are pushed onto an initially empty stack in this order, and pops may be interleaved with the pushes at any time. Which of the following output sequences is impossible?

A3 2 1 4
B4 3 2 1
C2 4 3 1
D3 1 2 4

Correct answer: D

Explanation

After 3 is popped the top of the stack is 2, so 2 must come out before 1; the sequence 3 1 2 4 is therefore impossible.

Join the discussion Report an error

Discussion 0

Nobody has replied yet. Start the discussion!