Question

The equivalent infix expression and value for the postfix form 1 2 + 3 * 4 5 * – will be ___________

(a) 1 + 2 * 3 – 4 * 5 and -13

(b) (2 + 1) * (3 – 4) * 5 and 13

(c) 1 + 2 * (3 – 4) * 5 and -11

(d) (1 + 2) * 3 – (4 * 5) and -11

My doubt stems from Application of Stacks topic in chapter Application of Stacks of Data Structures & Algorithms I

I have been asked this question in an interview for job.

Answer 1

Correct answer is (d) (1 + 2) * 3 – (4 * 5) and -11

Given postfix expression : 1 2 + 3 * 4 5 * –

⇒ (1 + 2) 3 * 4 5 * –

⇒ ((1 + 2) * 3) 4 5 * –

⇒ ((1 + 2) * 3) (4 * 5) –

⇒ ((1 + 2) * 3) – (4 * 5)

So, the equivalent infix expression is (1 + 2) * 3 – (4 * 5) and it’s value is -11.