Simulation

Subtitle / Summary LeetCode 2 is grade-school addition translated into a linked-list workflow. The only persistent state is the carry, and the only structural work is appending one new digit per round. Reading time: 12-15 min Tags: Hot100, linked list, carry, simulation SEO keywords: Add Two Numbers, linked-list carry, reverse order digits, LeetCode 2, Hot100 Meta description: A derivation-first ACERS guide to LeetCode 2 with carry propagation, dummy node construction, engineering mapping, and runnable multi-language code. A - Algorithm (Problem and Algorithm) Problem Restatement You are given two non-empty linked lists l1 and l2. Each list stores a non-negative integer in reverse order, and each node contains one digit. Add the two integers and return the sum as a linked list in the same reverse order. ...

Subtitle / Summary This problem is just grade-school addition on a linked list: add one digit at a time, propagate carry, and append one final node if carry remains after both lists end. We move from naive ideas to the optimal one-pass solution, then map it to real engineering scenarios. Reading time: 12-15 min Tags: linked list, carry, simulation, LeetCode 2 SEO keywords: Add Two Numbers, LeetCode 2, reverse-order list, carry, dummy node Meta description: Use dummy + tail + carry to sum two reverse-order linked lists in O(max(m,n)) time, with common pitfalls, engineering analogies, and six-language runnable implementations. A — Algorithm (Problem & Algorithm) Problem Restatement You are given two non-empty linked lists representing two non-negative integers. Digits are stored in reverse order, and each node stores one digit. Return their sum as a linked list in the same reverse order. Except for number 0, the input numbers do not have leading zeros. ...

Subtitle / Summary Spiral traversal looks like “just printing in a fancy order”, but the real difficulty is getting boundaries and invariants right. This ACERS guide gives a reusable boundary-shrinking template and runnable multi-language solutions. Reading time: 12–15 min Tags: Hot100, matrix, simulation, boundary shrinking SEO keywords: Hot100, Spiral Matrix, clockwise traversal, boundary shrinking, LeetCode 54 Meta description: O(mn) spiral order traversal using boundary shrinking, with pitfalls, engineering scenarios, and runnable code. A — Algorithm Problem Restatement Given an m × n matrix matrix, return all elements in clockwise spiral order. ...