Stack + Monotonic — Reasoning Check

1. What is the largest histogram rectangle area for heights [3,1,3,3]? Enter one integer.

2. Daily Temperatures processes [72,71,71,73]. Why must both 71 indices remain pending until 73 arrives?

Select one answer.

An equal temperature does not answer a strictly-warmer query, and the two indices have different waiting times. Equal temperatures can be represented by one index because their waits are equal. The second 71 resolves the first because nondecreasing temperature counts as warmer.

3. Evaluate postfix tokens ["9","4","-","2","/"], using integer division toward zero. Enter one integer.

4. A Min Stack stores one uncounted copy of each new minimum in a second stack. After Push(5), Push(2), Push(2), Pop(), GetMin returns 5. What information was lost?

Select one answer.

Pop should remove every equal value to keep the stack monotonic. One occurrence of minimum 2 remains and must still be represented. The original maximum 5 should have been discarded permanently.

5. Evaluate 8-(3-(2-5)). Enter one integer.

6. A histogram implementation pops only when the incoming bar is STRICTLY lower and never performs a final flush. Which input exposes its missing work?

Select one answer.

[1,2,3], because every positive bar can remain unresolved after the last arrival. [0], because zero-height bars must contribute positive area. [3,2,1], because every bar is finalized before its right boundary exists.