Hot100: Intersection of Two Linked Lists Two-Pointer Switch-Head O(1) Space ACERS Guide
Subtitle / Summary The key is not comparing values, but comparing node identity (same object / same address). This ACERS guide explains the naive hash approach, the length-alignment approach, and the most practical switch-head two-pointer template, with runnable multi-language implementations under the no-modification and no-cycle constraints. Reading time: 10-14 min Tags: Hot100, linked list, two pointers SEO keywords: Intersection of Two Linked Lists, switch heads, O(1) space, LeetCode 160 Meta description: Two pointers walk A then B and B then A, guaranteeing meeting at the intersection or both reaching null within m+n steps, with O(m+n) time and O(1) space. Target Readers Hot100 learners who want a reusable linked-list two-pointer template Developers who often confuse “same value” with “same node” Engineers working with shared tail structures in chain-like data Background / Motivation This problem looks simple, but it forces you to separate three concepts: ...