Clarify the problem constraints (e.g., singly linked lists, intersection by reference, no cycles) and discuss trade-offs between approaches. Present an optimal solution like the two-pointer technique that achieves O(m+n) time and O(1) space, and walk through an example to demonstrate correctness.
Pro tip: Emphasize that intersection is determined by node reference, not value, and mention that the two-pointer approach elegantly handles unequal list lengths without explicit length calculation. This shows attention to detail and algorithmic maturity.
Ask clarifying questions: Are the lists singly linked? Can they have cycles? Is intersection defined by reference or value? What should be returned if no intersection exists?
Outline possible solutions: brute force with nested loops (O(m*n)), hash set to store visited nodes (O(m+n) time, O(m) space), and the optimal two-pointer technique (O(m+n) time, O(1) space).
Detail the two-pointer method: initialize pointers at each head, traverse simultaneously, and when one reaches the end, redirect it to the other list's head. They will meet at the intersection node or both become null if no intersection.
Use a concrete example with lists of different lengths to illustrate how the pointers align after switching heads, ensuring they traverse the same total distance and meet at the intersection.
State time complexity O(m+n) and space O(1). Discuss edge cases: empty lists, no intersection, intersection at head, and lists of equal length.
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