Recognise the pattern.Then solve.
Lessgo is the prep system for software interviews. 1,294 problems, 49 patterns and every company loop — in one plan that remembers what you’re about to forget.
Problem
Given a sorted array of integers, return the indices of two numbers that add up to target, using O(1) extra space.
- 01order lets you discard a whole side
- 02a pair search
- 03no hash map — move indices instead
Pattern
Why Lessgo
Most prep is five hundred random problems and a spreadsheet. You solve, you forget, and on the day it’s a blank page. Lessgo is built around how recall actually works: recognise the shape, climb the ladder, review right before you’d forget.
The method
Three loops. One system.
01 · Recognise
Every pattern has a tell.
“Sorted array, find a pair” is two pointers before you’ve read the constraints. Lessgo teaches the signal for each of the 49 patterns, so the first minute of a round goes to the right idea — not a guess.
Sorted array; find a pair / triplet hitting a target, or shrink from both ends
Two Pointers
Contiguous subarray/substring asked to be longest/shortest/max/min under a constraint
Sliding Window
"Subarray sum equals k" / "divisible by k", or many range-sum queries
Prefix Sum + HashMap
A linked list that might have a cycle, or you need the middle in one pass
Fast & Slow Pointers
Reverse a list, a sublist, or every k nodes — O(1) extra space
In-place LL Reversal
Intervals / ranges that may overlap: merge, insert, or count rooms/conflicts
Merge Intervals
02 · Practise
Ladders, not lists.
Each pattern comes with a graded ladder that climbs from the canonical problem to the one that shows up in onsites — drawn from LeetCode, CSES, Codeforces and reported OAs.
Two Pointers
ladder · 3 / 7
- Valid Palindrome
- Two Sum II - Input Array Is Sorted
- 3Sum
- Sort Colors
- Container With Most Water
- Trapping Rain Water
- Concatenation of Array
03 · Remember
Review right before you forget.
Rate how a solve felt and Lessgo schedules the next review on a spaced-repetition curve. Weak spots surface on their own; strong ones get out of your way.
Recall over 30 days
next review · day 14
Sorted array; find a pair / triplet hitting a target, or shrink from both ends
Two Pointers
Contiguous subarray/substring asked to be longest/shortest/max/min under a constraint
Sliding Window
"Subarray sum equals k" / "divisible by k", or many range-sum queries
Prefix Sum + HashMap
A linked list that might have a cycle, or you need the middle in one pass
Fast & Slow Pointers
Reverse a list, a sublist, or every k nodes — O(1) extra space
In-place LL Reversal
Intervals / ranges that may overlap: merge, insert, or count rooms/conflicts
Merge Intervals
NewAscend
Climb a pattern from E to S.
Pick a pattern. Climb it.
Every pattern is a path of nine steps. Each one is the last problem plus a single twist.
The map
Every pattern, connected.
49 patterns in 16 families. Lessgo knows what each one builds on and what it gets mistaken for — so you learn them in an order that compounds.
Hover or tap any point on the map.
49
patterns
The journey
From first pattern to signed offer.
A roadmap that sequences the work so each week builds on the last — and tells you when you’re ready.
01
Concepts
28 toolkit topics: data structures, syntax and complexity.
02
Patterns
49 patterns in 16 categories, each with a signal and a template.
03
Problems
1,294 problems across LeetCode, CSES, Codeforces and OAs.
04
Revision
Spaced repetition schedules every solve. Weak spots surface on their own.
05
Rounds
System design, core CS and behavioural — rehearsed, not winged.
06
Offer
Readiness scores tell you when you’re there, not just how busy you’ve been.
Coverage
Everything you’d otherwise tab between.
- 0
- Problems
- 0
- Patterns
- 0
- CSES problems
- 0
- Codeforces ladder
- 0
- Company loops
- 0
- OA questions
One tracker, every source
Across 16 categories
The full competitive set
Rated 800 → 2400
Rounds, frequency and plans
Reported online assessments
0%
OA ready
0%
Interview ready
6
reviews due
14d
streak
3/3
today
Company loops
Every loop, mapped.
Rounds, what interviewers listen for, question frequency, and a 7, 14 or 30-day plan — for 40 companies.
Browse companiesFrom the people using it
“I stopped doing random problems. Two weeks of pattern ladders and the OA questions started to look familiar.”
“The review queue is the part I didn’t know I needed. It brings back exactly the problems I’d half-forgotten.”
“I built Lessgo because I kept forgetting problems I’d already solved. Now the plan remembers for me.”
Your interview is already on the calendar.
Start with one pattern today. Lessgo will tell you what comes next.