// Compete

Ranked coding practice that actually feels alive.

1v1 battles anchor the lane. Puzzle Rush, guided practice, mock interviews, and personal-best ghosts give you useful reps when you are not queueing.

Enter matchmaking View rankings

https://algoarena.net/lobby

Exit BattleLIVE BATTLE

Battle Lobby

Finding you a worthy opponent...

Searching for opponent

Looking for someone near your skill level.

Problem difficulty is set from your ranked Elo and your opponent's when a match is found. No extra setup needed.

Elapsed

0:00

Ranked Elo band

625-675

Est. time remaining 00:20

Scanning for opponents in your skill range...

10,000+

Problems

curated CS practice items

Languages

Python to Rust, consistent judging

Elo

Ranked 1v1

live human duels

Modes

Solo pressure

Puzzle Rush, guided practice, and self-ghosts

Supporting modes

Train even when you are not in a duel.

The live battle IDE stays the flagship. These modes keep the reps useful when you want coaching, speed, or a personal-best race.

Guided practice

Train with Rena when you do not want a duel.

Hint-mode Rena coaches edge cases, syntax, and test discipline without turning the rep into a live match.

Practice with hints

Back to Practice

Problem List

15:35

Time Remaining

Hide Timer

Code

1# Starport Access Code
2import sys
3 
4data = sys.stdin.read().split()
5t = int(data[0])
6ptr = 1
7 
8for _ in range(t):
9    n = int(data[ptr])
10    s = data[ptr + 1]
11    ptr += 2
12 
13    possible = False
14    for i, ch in enumerate(s):
15        if ch == "8" and n - i == 11:
16            possible = True
17            break
18 
19    print("YES" if possible else "NO")

Ln 1, Col 23Spaces: 4

Test Result0/3 Passed (0%)

Testcase

Input

1
11
80011223388

Your Output

Pending...

Expected

YES

All 3 public test cases shown

Puzzle Rush

Trace faster. Think sharper.

Short logic rounds use their own Puzzle Rush rating, separate from ranked Elo.

Start a rush

Puzzle Rush 3 min

Puzzle Battle

Pick a rush length

Fast CS puzzles, one opponent, score pressure from the first question.

Ghost Time Trials

Race past-you for a cleaner personal best.

Self-ghosts add solo pressure, practice XP, and shareable receipts while ranked Elo stays untouched.

Start a time trial

Solo pressure02:38

You now9/11

86% complete

Past youghost

74% complete

Ghost receipt

Personal best within reach.

Elo unchangedXP pending

Skill loop

The product rewards clear practice, not just speed.

Problem library

Topic coverage across core CS.

Arrays, graphs, DP, strings, heaps, search, and more remain accessible from the practice lane.

Explore topics

Practice library10,000+ problems

binary search, graphs, dp...

Arrays

1,420

Graphs

980

760

Strings

1,110

Count Set Bits

Easy

950

Shortest Safe Path

Medium

1450

Warehouse Intervals

Hard

2100

Mock interviews

Practice explaining your approach.

Interview-style sessions train how you reason, verify, and talk through the work.

Start interview prep

AI Interviewer

Interview Active

📖 Reading Time:Starting soon...

Timer will start after the introduction

Speaking...

Clara

Speaking…

Hello, I'm Clara, your AI interviewer. Please take your time to read and understand the problem. You have about 3 minutes to read through it. I'll check back with you when the time is up. Good luck!

Clara is speaking...

Please read the problem first...

Input blocked during reading

AI fluency

Use AI without skipping the thinking.

Guided practice and interview prep reward clear reasoning, test discipline, and explanation.

Try guided practice

Back to Practice

Problem List

15:35

Time Remaining

Hide Timer

Code

1# Starport Access Code
2import sys
3 
4data = sys.stdin.read().split()
5t = int(data[0])
6ptr = 1
7 
8for _ in range(t):
9    n = int(data[ptr])
10    s = data[ptr + 1]
11    ptr += 2
12 
13    possible = False
14    for i, ch in enumerate(s):
15        if ch == "8" and n - i == 11:
16            possible = True
17            break
18 
19    print("YES" if possible else "NO")

Ln 1, Col 23Spaces: 4

Test Result0/3 Passed (0%)

Testcase

Input

1
11
80011223388

Your Output

Pending...

Expected

YES

All 3 public test cases shown

Connected product family

Compete is the training ground for the rest of AlgoArena.

Classroom handoff

The same practice loop can power class.

Educators can turn competitive practice into live teaching sessions and reviewable outcomes.

Explore Classroom

Practice library10,000+ problems

binary search, graphs, dp...

Arrays

1,420

Graphs

980

760

Strings

1,110

Count Set Bits

Easy

950

Shortest Safe Path

Medium

1450

Warehouse Intervals

Hard

2100

Hiring handoff

Practice becomes assessable evidence.

The skills trained here connect directly to future assessment evidence for AI-era work.

Preview Assessments

AI Interviewer

Interview Active

📖 Reading Time:Starting soon...

Timer will start after the introduction

Speaking...

Clara

Speaking…

Hello, I'm Clara, your AI interviewer. Please take your time to read and understand the problem. You have about 3 minutes to read through it. I'll check back with you when the time is up. Good luck!

Clara is speaking...

Please read the problem first...

Input blocked during reading

Vibecoding Courses handoff

Plain-English learners can graduate into code.

Vibecoding Courses start without syntax, then point learners toward real practice and competition.

Preview Vibecoding Courses

Practice library10,000+ problems

binary search, graphs, dp...

Arrays

1,420

Graphs

980

760

Strings

1,110

Count Set Bits

Easy

950

Shortest Safe Path

Medium

1450

Warehouse Intervals

Hard

2100

Recent from the field notes

All field notes

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You can grind LeetCode forever and still freeze in a live interview. Performance under pressure is its own skill, and you can only train it under pressure.

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How the 90-node campaign, medal progress, and ranked ghosts turn practice into a visible progression loop.

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Assessments2026-06-22

AI-Native Assessments Need Evidence, Not Theater

Why the new assessment scoring model focuses on competencies, browser evidence, verification, and reviewer-visible artifacts instead of pretending AI disappeared.

Read

Classroom2026-06-15

Bounded AI Practice in the Classroom

A field note on hint-only Rena, teacher-controlled AI modes, and why classroom assistance should coach thinking without handing over solutions.

Read

Start concrete

Battle in the same workspace you practice in.

It shows the whole loop in one glance: problem, editor, opponent, tests, submit, and progress. The newer product lanes should inherit this same clarity as they mature.

Find a match