Interview questions

Longest Path With Different Adjacent Characters

Find the longest simple path in a rooted tree where every pair of adjacent nodes have different characters; this is solved with a DFS/tree-DP that…

General practice

Longest Repeating Substring

Given a string, return the length of the longest substring that appears at least twice in the string (overlaps allowed). This requires efficiently detecting repeated…

General practice

Longest Resilient Subarray I

General practice

Longest Resilient Subarray II

General practice

Longest Semi-Repeating Subarray

Find the length of the longest contiguous subarray (or substring) that is "semi-repeating" — i.e., contains at most one value/character that appears more than once…

General practice

Longest Special Path

Given a rooted weighted tree with a value at each node, find a downward ancestor→descendant path whose node values are all unique that maximizes the…

General practice

Longest Special Path II

Given a rooted tree with edge lengths and node values, find a downward ancestor→descendant path that maximizes total edge length under the constraint that node…

General practice

Longest Square Streak in an Array

Find the maximum length (≥2) subsequence of nums whose elements, when sorted, form a chain a, a^2, a^4, ... (each element is the square of…

General practice

Longest Strictly Increasing or Strictly Decreasing Subarray

Given an integer array, return the length of the longest contiguous subarray that is strictly increasing or strictly decreasing. This is equivalent to finding the…

General practice

Longest Strictly Increasing Subsequence With Non-Zero Bitwise AND

General practice

Longest Subarray Divisible by K with At Most One Negation I

Companies: Amazon

Array · Hash Table · Prefix Sum

Longest Subarray Divisible by K with At Most One Negation II

General practice

Longest Subarray of 1's After Deleting One Element

Given a binary array, delete exactly one element and return the length of the longest contiguous subarray of 1s in the resulting array (0 if…

General practice

Longest Subarray With at Most K Distinct Prime Factors

General practice

Longest Subarray With Maximum Bitwise AND

Find the maximum bitwise AND achievable by any subarray and return the length of the longest contiguous subarray that attains it. Key observation: the maximum…

General practice

Longest Subarray With Restricted Pair Sums

General practice

Longest Subsequence Repeated k Times

Find the longest string seq such that seq repeated k times (seq*k) is a subsequence of s, returning the lexicographically largest one on ties (or…

General practice

Longest Subsequence With Decreasing Adjacent Difference

Find the longest subsequence of nums such that the absolute differences between consecutive chosen elements are non-increasing. This is an LIS-like DP problem where you…

General practice

Longest Subsequence With Limited Sum

For each query, determine the maximum number of elements you can pick from nums (as a subsequence) whose sum is ≤ query — equivalent to…

General practice

Longest Subsequence With Non-Zero Bitwise XOR

Companies: Bloomberg, Google, Infosys

Array · Bit Manipulation

Longest Substring Of All Vowels in Order

Find the length of the longest contiguous substring made only of vowels that contains each of 'a','e','i','o','u' at least once and whose characters never decrease…

Companies: Rippling

Sliding Window · String

Longest Substring with At Least K Repeating Characters

Find the length of the longest substring of a lowercase string s such that every character in that substring appears at least k times. The…

General practice