Starlight: List of Problems

Over 20,000 problems available. AMC 8/10/12 and AIME problems from 2010-2023; USAJMO/USAMO problems from 2002-2023 available. USACO problems from 2014 to 2023 (all divisions). Codeforces, AtCoder, DMOJ problems are added daily around 04:00 AM UTC, which may cause disruptions.

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AMC 8: [year] AMC 8 Problem #, Ex: 2013 AMC 8 Problem 1
AMC 10: [year] AMC 10A Problem # OR [year] AMC 10B Problem #, Ex: 2015 AMC 10A Problem 16
AMC 12: [year] AMC 12A Problem # OR [year] AMC 12B Problem #, Ex: 2021 AMC 12B Problem 25
AIME: [year] AIME I Problem # OR [year] AIME II Problem #, Ex: 2013 AIME I Problem 8
USAJMO/USAMO: [year] USAJMO/USAMO Problem #, Ex: 2023 USAJMO Problem 1
Codeforces: Codeforces [contest id (e.g. 101)][problem id (e.g. A, B, C)]: [Codeforces problem name], Ex: Codeforces 1336F: Journey
AtCoder: AtCoder [contest id (e.g. ABC314, ARC164, ZONE2021)]: [problem id (A, B, C)]. [Problem name], Ex: AtCoder ZONE2021: E. Sneaking
DMOJ: DMOJ [contest name (if applicable)] [problem number (e.g. P1)] - [Problem name], Ex: DMOJ Yet Another Contest 3 P1 - Shell Swap Scam
USACO: [year] [contest month (e.g. January, US Open)], [division (e.g. Gold)]: [Problem name], Ex: USACO 2023 US Open Contest, Bronze: Rotate and Shift

ID	Problem Name (click to add insights/hints, view summary of insights/hints and similar problems)
1251	Codeforces 275A: Lights Out
1250	Codeforces 274E: Mirror Room
1249	Codeforces 274D: Lovely Matrix
1248	Codeforces 274C: The Last Hole!
1247	Codeforces 274B: Zero Tree
1246	Codeforces 274A: k-Multiple Free Set
1245	Codeforces 273E: Dima and Game
1244	Codeforces 273D: Dima and Figure
1243	Codeforces 272E: Dima and Horses
1242	Codeforces 272D: Dima and Two Sequences
1241	Codeforces 272C: Dima and Staircase
1240	Codeforces 272B: Dima and Sequence
1239	Codeforces 272A: Dima and Friends
1238	Codeforces 271E: Three Horses
1237	Codeforces 271D: Good Substrings
1236	Codeforces 271C: Secret
1235	Codeforces 271B: Prime Matrix
1234	Codeforces 271A: Beautiful Year
1233	Codeforces 270B: Multithreading
1232	Codeforces 270A: Fancy Fence
1231	Codeforces 269E: String Theory
1230	Codeforces 269D: Maximum Waterfall
1229	Codeforces 269C: Flawed Flow
1228	Codeforces 269B: Greenhouse Effect
1227	Codeforces 269A: Magical Boxes
1226	Codeforces 268E: Playlist
1225	Codeforces 268D: Wall Bars
1224	Codeforces 268C: Beautiful Sets of Points
1223	Codeforces 268B: Buttons
1222	Codeforces 268A: Games
1221	Codeforces 267C: Berland Traffic
1220	Codeforces 267B: Dominoes
1219	Codeforces 267A: Subtractions
1218	Codeforces 266E: More Queries to Array...
1217	Codeforces 266D: BerDonalds
1216	Codeforces 266C: Below the Diagonal
1215	Codeforces 266B: Queue at the School
1214	Codeforces 266A: Stones on the Table
1213	Codeforces 265B: Roadside Trees (Simplified Edition)
1212	Codeforces 265A: Colorful Stones (Simplified Edition)
1211	Codeforces 264E: Roadside Trees
1210	Codeforces 264D: Colorful Stones
1209	Codeforces 264C: Choosing Balls
1208	Codeforces 264B: Good Sequences
1207	Codeforces 264A: Escape from Stones
1206	Codeforces 263E: Rhombus
1205	Codeforces 263D: Cycle in Graph
1204	Codeforces 263C: Circle of Numbers
1203	Codeforces 263B: Squares
1202	Codeforces 263A: Beautiful Matrix

Problem Name (click to add insights/hints, view summary of insights/hints and similar problems)

1251

Codeforces 275A: Lights Out

1250

Codeforces 274E: Mirror Room

1249

Codeforces 274D: Lovely Matrix

1248

Codeforces 274C: The Last Hole!

1247

Codeforces 274B: Zero Tree

1246