Crack the coding interview,
one problem at a time.
Curated lists, an in-browser Python and JavaScript editor, complexity estimates, progressive hints, plus DSA primers and a system-design course — all running locally, nothing to sign up for.
2837 problems 2 curated lists 0 backends
lytecode.dev/problems/two-sum
1. Two Sum Easy
Return indices of the two numbers such that they add up to target.
Array Hash Table
def twoSum(nums, target):
# O(n) hash map
seen = {}
for i, n in enumerate(nums):
✓ Accepted 52 ms · O(n) time · O(n) space
Run code in your browser
Python (via Pyodide) and JavaScript, all in your browser — no install, no backend.
See your complexity
An empirical, best-effort Big-O estimate from real timing samples.
AI coach
An optional coach that runs and debugs your code, explains approaches, and reviews solutions.
Mock interviews
Practice talking through your approach under time, with an AI interviewer driving the session.
Versus mode (alpha)
Race a random opponent — or a friend — to solve the same problem first: a Matiks/NeetCode-style code-solving duel. In alpha, so expect bugs.
Learn the patterns
Short DSA primers and a chaptered system-design course — read one, then go solve.
Your data stays yours
Notes and favorites are saved to your device with OPFS.
Start with a proven list
Hand-picked sets that cover every interview pattern.