Intersection Detection — Linked List Manipulation Patterns
The Intersection Detection pattern applies when you need the Intersection Detection technique within the Linked List Manipulation Patterns pattern. Its time complexity is O(m + n) and space complexity O(1). It is used in 2 problems on Thita, including Intersection of Two Linked Lists and Minimum Index Sum of Two Lists. Common variations are Reordering / Partitioning and In-place Reversal.
Learn to find the intersection point of two linked lists using the two-pointer technique.
Intersection Detection is one of the 5 subpatterns of the Linked List Manipulation Patterns pattern, which covers in-place reversal, merging sorted lists, reordering, and intersection detection. The whole pattern is about 2 hours of study. This subpattern is a depth topic for once the core techniques are automatic.
What Intersection Detection covers
Master linked list manipulation including in-place reversal, merging sorted lists, detecting intersections, and reordering. Essential pointer manipulation techniques for interviews. Problems in this subpattern are usually searched for as intersection linked list, find intersection, list intersection, two pointer, leetcode 160.
How to practise Intersection Detection on Thita.ai
Read the theory for Intersection Detection, then work the problems attached to it in the browser editor. Your solution runs against the problem's test cases, and the AI coach offers a hint about the technique you are missing rather than a finished solution. Progress is tracked per subpattern, so the Linked List Manipulation Patterns tracker shows this one as covered once you have solved its problems.
Other subpatterns in Linked List Manipulation Patterns
- In-place Reversal — Master in-place linked list reversal including full reversal, partial reversal, and k-group reversal techniques.
- Merging Two Sorted Lists — Learn to merge two sorted linked lists efficiently. Foundation for merge sort and k-way merge problems.
- Reordering / Partitioning — Learn to reorder and partition linked lists. Master techniques like swap pairs, rotate list, and odd-even separation.
- Addition of Numbers — Master adding numbers represented as linked lists. Handle carry operations and different list lengths.
Related DSA patterns
- Binary Search Patterns — Standard binary search, rotated arrays, first/last occurrence, and search on answer space.
- Array/Matrix Manipulation Patterns — In-place operations, hashing, prefix sums, spiral traversal, and cyclic sort.
- Stack Patterns — Parentheses matching, monotonic stack, histogram, and expression evaluation.
- String Manipulation Patterns — Palindrome checking, anagram detection, pattern matching, and string conversion.
Where to go next
Intersection Detection is one lesson in a 16-pattern DSA course. If you are preparing end to end, work the interview-critical patterns first and use the pattern sheet as the checklist; if you are here for one technique, the Linked List Manipulation Patterns guide is the shortest path back to the rest of it.