[Solved] Examine the following buggy code for interval intersections: def intervalIntersection(A, B): i, j = 0, 0 result = [] while i < len(A) and j < len(B): if A[i][1] <= B[j][0]:... | Intervals

Intervals - Interval List Intersections

Examine the following buggy code for interval intersections:

def intervalIntersection(A, B):
    i, j = 0, 0
    result = []
    while i < len(A) and j < len(B):
        if A[i][1] <= B[j][0]:
            i += 1
        elif B[j][1] < A[i][0]:
            j += 1
        else:
            start = max(A[i][0], B[j][0])
            end = min(A[i][1], B[j][1])
            result.append([start, end])
            if A[i][1] < B[j][1]:
                i += 1
            else:
                j += 1
    return result

What is the bug in this code?

AThe condition 'if A[i][1] <= B[j][0]' should use '<' instead of '<=' to correctly detect touching intervals.

BThe pointer increments inside the else block are reversed; they should increment the pointer with the larger endpoint.

CThe overlap condition should check 'start < end' instead of 'start <= end' to avoid zero-length intervals.

DThe code does not handle empty input lists, which can cause runtime errors.

Step-by-Step Solution

Step 1: Analyze overlap condition
Using '<=' excludes intervals that touch at a point (e.g., end == start), missing valid intersections.
Step 2: Correct condition
Changing to '<' ensures intervals that share a boundary point are considered intersecting.
Final Answer:
Option A -> Option A
Quick Check:
Inclusive endpoints require '<' not '<=' to detect touching intervals [OK]

Quick Trick: Check boundary conditions carefully for inclusive intervals [OK]

Common Mistakes:

MISTAKES

Using <= instead of <
Reversing pointer increments
Ignoring empty inputs

Trap Explanation:

PITFALL

Using '<=' looks safer but misses intersections where intervals just touch at a point.

Interviewer Note:

CONTEXT

Tests attention to subtle boundary conditions in interval comparisons.

Master "Interval List Intersections" in Intervals

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More Intervals Quizzes

Examine the following buggy code for interval intersections:

Step 1: Analyze overlap condition

Step 2: Correct condition

Final Answer:

Quick Check:

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