Stacks and Queues Important Questions

Important points

• Balanced parantheses
• Next smaller/greater element to the left/right
• Sliding window maximum
• queue using two stacks and stack using 2 queues
• Stack = LIFO, Queue = FIFO

Easy/Medium (MUST DO)

• https://practice.geeksforgeeks.org/problems/queue-using-two-stacks/1 (IMPORTANT asked a lot in MCQs (for ex. Amazon))
• https://practice.geeksforgeeks.org/problems/stack-using-two-queues/1
• https://practice.geeksforgeeks.org/problems/parenthesis-checker/0 (Standard question for stacks)
• https://practice.geeksforgeeks.org/problems/get-minimum-element-from-stack/1 (IMPORTANT asked a number of times)
• https://www.interviewbit.com/problems/rain-water-trapped/ (IMPORTANT)
• https://leetcode.com/problems/simplify-path/
• https://leetcode.com/problems/moving-average-from-data-stream/
• https://leetcode.com/problems/design-circular-queue/ (IMPORTANT handle edge cases properply)

Hard

• https://www.interviewbit.com/problems/sliding-window-maximum/ (IMPORTANT)
• https://www.interviewbit.com/problems/largest-rectangle-in-histogram/
• https://www.interviewbit.com/problems/nearest-smaller-element/ (MOST IMPORTANT FOR STACKS)
• https://leetcode.com/problems/next-greater-node-in-linked-list/
• https://leetcode.com/problems/daily-temperatures/
• https://leetcode.com/problems/decode-string/ (IMPORTANT will require a bit of thinking)
• https://leetcode.com/problems/evaluate-reverse-polish-notation/