Given a list of train arrival and departure times, which technique efficiently determines the minimum number of platforms needed to avoid any waiting time?

easy💻 Programming Q1 of Q15

Greedy Algorithms - Minimum Platforms (Train Stations)

ASorting arrivals and departures separately and using two pointers to count overlaps

BDynamic programming to find the longest non-overlapping intervals

CDepth-first search on a graph representing train schedules

DBinary search on sorted departure times for each arrival

Step-by-Step Solution

Solution:

Step 1: Sort arrival and departure arrays
Sorting helps to process events in chronological order.
Step 2: Use two pointers to traverse arrivals and departures
Increment platform count when a train arrives before the earliest departure, decrement when a train departs.
Final Answer:
Option A -> Option A
Quick Check:
Counting overlapping intervals with sorted arrays [OK]

Quick Trick: Sort and count overlaps with two pointers [OK]

Common Mistakes:

MISTAKES

Using dynamic programming which is unnecessary here
Applying graph traversal which complicates the problem
Using binary search per arrival which is inefficient

Trap Explanation:

PITFALL

Dynamic programming or graph methods seem plausible but are inefficient for this problem.

Interviewer Note:

CONTEXT

Tests understanding of interval overlap and greedy algorithm application.

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More Greedy Algorithms Quizzes

Given a list of train arrival and departure times, which technique efficiently determines the minimum number of platforms needed to avoid any waiting time?

Step 1: Sort arrival and departure arrays

Step 2: Use two pointers to traverse arrivals and departures

Final Answer:

Quick Check:

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