7 articles
LeetCode 647 Palindromic Substrings is the canonical center-expansion problem. We derive the 2D DP recurrence, simplify it to expand-around-center for O(1) memory, and walk through a full DP table dry run with FAANG interview tips on why this beats Manacher in real interviews.
LeetCode 516 Longest Palindromic Subsequence is the cleanest interval DP recurrence in interview prep. We derive the dp[i][j] formulation, fill the table along diagonals, and reduce memory from O(n^2) to O(n) — exactly the depth Amazon and Google look for.
LC 234 Palindrome Linked List is a popular interview problem at Facebook, Amazon, and Apple that combines three core techniques: fast/slow pointer midpoint finding, in-place list reversal, and two-pointer comparison. Master the O(1) space solution with Python and JavaScript code and a step-by-step dry run.
Manacher finds the longest palindromic substring in O(n) by exploiting palindrome symmetry to skip redundant character comparisons. The same mirror trick that powers the Z algorithm, applied to the palindrome radius array.
Longest Palindromic Substring, Palindrome Partitioning, and Palindromic Substrings form a tight family of FAANG questions. Master expand-around-center, 2D DP, and the link to Manacher and you can adapt to any variant on the spot.
Shortest Palindrome (LC 214) is a hard FAANG problem that hides a classic KMP application. Concatenate s with reversed(s) and the failure function reveals the longest palindromic prefix in linear time. Master this trick and you unlock half a dozen related KMP applications.
LeetCode 336 — find every pair (i,j) such that words[i] + words[j] is a palindrome. The trie solution stores reversed words and tags palindrome-suffix indices, enabling O((N times K^2)) lookup.