Bird
Raised Fist0

Identify the line containing the subtle bug that causes incorrect results for intervals that just touch (e.g., [1,5] and [5,10]).

medium🐞 Bug Identification Q14 of Q15
Intervals - Meeting Rooms I
The following code attempts to determine if a person can attend all meetings. Identify the line containing the subtle bug that causes incorrect results for intervals that just touch (e.g., [1,5] and [5,10]).
from typing import List

def can_attend_meetings(intervals: List[List[int]]) -> bool:
    intervals.sort(key=lambda x: x[0])
    end = float('-inf')
    for interval in intervals:
        if interval[0] <= end:
            return False
        end = interval[1]
    return True
ALine 6: if interval[0] <= end:
BLine 3: intervals.sort(key=lambda x: x[0])
CLine 5: for interval in intervals:
DLine 7: end = interval[1]
Step-by-Step Solution
  1. Step 1: Understand the overlap condition

    Meetings that just touch (e.g., end=5 and start=5) should not be considered overlapping.
  2. Step 2: Identify the bug

    The condition uses <= which incorrectly treats touching intervals as overlapping. It should use < instead.
  3. Final Answer:

    Option A -> Option A
  4. Quick Check:

    Changing <= to < fixes false positives on touching intervals [OK]
Quick Trick: Overlap check must use <, not <= [OK]
Common Mistakes:
MISTAKES
  • Using <= causes false overlap detection on touching intervals
Trap Explanation:
PITFALL
  • Using <= looks correct but breaks correctness on edge cases where meetings end and start at the same time.
Interviewer Note:
CONTEXT
  • Tests attention to boundary conditions and subtle off-by-one bugs in interval comparisons.
Master "Meeting Rooms I" in Intervals

3 interactive learning modes - each teaches the same concept differently

Want More Practice?

15+ quiz questions · All difficulty levels · Free

Free Signup - Practice All Questions
More Intervals Quizzes