Citadel

4 problems asked at Citadel.

Easy (1)

Two Sum (Leetcode 1)

Two Pointers, Arrays

Medium (1)

Min Stack (Leetcode 155)

Stack

Hard (2)

Postfix to Infix & Evaluation of Postfix (Leetcode 150)

Stack

Trapping Rain Water (LC 42)

Two Pointers, Prefix and Suffix Arrays, Stack