±1

2-sat, dfs and similar, graphs

Arithmancy (Easy)

brute force, constructive algorithms, interactive, strings

Exact Neighbours (Medium)

constructive algorithms

Clique Partition

brute force, constructive algorithms, graphs, greedy, implementation

Learning to Paint

binary search, data structures, dfs and similar, dp, greedy, implementation, sortings

There and Back Again

XOR Break --- Solo Version

bitmasks, constructive algorithms, greedy

Turtle Mission: Robot and the Earthquake

dfs and similar, dp, graphs, shortest paths

Sum over all Substrings (Hard Version)

bitmasks, divide and conquer, dp, dsu, greedy, implementation, strings

Space Harbour

data structures, implementation, math, sortings

Counting Binary Strings

combinatorics, dp, math

01 Tree

constructive algorithms, data structures, dsu, greedy, sortings, trees

Light Bulbs (Easy Version)

brute force, combinatorics, dfs and similar, dp, dsu, graphs, math, trees

Array Collapse

data structures, divide and conquer, dp, trees

Blueprint for Seating

combinatorics, divide and conquer, math

Maximum Sum Subarrays

*special problem, dp

Count BFS Graph

combinatorics, dp

Maximize The Value

data structures, sortings

Transitive Graph

dfs and similar, dp, dsu, graphs, implementation

Permutation Sorting

data structures, sortings

Monocarp and the Set

combinatorics, data structures, math

Counting Rhyme

dp, math, number theory

Autosynthesis

constructive algorithms, dfs and similar, graphs, greedy, sortings

Candy Party (Hard Version)

bitmasks, constructive algorithms, dp, greedy, implementation, math

Happy Sets

combinatorics

Grouped Carriages

binary search, data structures, dp, flows, greedy

Guess Game

bitmasks, data structures, games, math, probabilities, sortings, strings, trees

Speedrun

brute force, dfs and similar, dp, graphs, greedy, math, sortings, two pointers

More Wrong

divide and conquer, interactive

Ball Sorting

data structures, dp, sortings

Bracket Walk

data structures, greedy, strings

Red-Blue Operations (Easy Version)

binary search, greedy, implementation, math

Rearrange Brackets

brute force, dp, greedy, sortings, strings

Vlad and the Nice Paths (easy version)

combinatorics, dp, math

Is It Flower?

dfs and similar, graphs, implementation

Monsters

brute force, data structures, dfs and similar, dsu, graphs, greedy

Petya, Petya, Petr, and Palindromes

binary search, brute force, data structures, two pointers

The way home

binary search, data structures, dp, graphs, greedy, shortest paths, sortings

Hot Start Up (hard version)

data structures, dp

Timofey and Black-White Tree

brute force, dfs and similar, divide and conquer, graphs, greedy, math, shortest paths, trees

The Harmonization of XOR

bitmasks, constructive algorithms, greedy, math

Flexible String Revisit

combinatorics, dp, math, probabilities

Another Wine Tasting Event

combinatorics, constructive algorithms, math, strings

The Human Equation

greedy, implementation

Hossam and (sub-)palindromic tree

brute force, data structures, dfs and similar, dp, strings, trees

Count Binary Strings

data structures, dp

GCD Queries

constructive algorithms, interactive, number theory

Carry Bit

combinatorics, math

ConstructOR

bitmasks, chinese remainder theorem, combinatorics, constructive algorithms, math, number theory

Rectangular Congruence

constructive algorithms, number theory

Sheikh (Hard Version)

binary search, bitmasks, brute force, greedy, implementation, two pointers

Cut Substrings

combinatorics, dp, hashing, strings, two pointers

Field Photography

bitmasks, data structures, sortings

Rain

binary search, brute force, data structures, geometry, greedy, implementation, math

MEX vs DIFF

binary search, brute force, constructive algorithms, data structures, greedy, two pointers

Preorder

combinatorics, divide and conquer, dp, dsu, hashing, sortings, trees

Optimal Partition

data structures, dp

Job Lookup

constructive algorithms, dp, shortest paths, trees

Promising String (hard version)

data structures, implementation, math, strings

Potion Brewing Class

dfs and similar, math, number theory, trees

Counting Shortcuts

data structures, dfs and similar, dp, graphs, shortest paths

Best Pair

binary search, brute force, implementation

Game on Sum (Easy Version)

combinatorics, dp, games, math

Martial Arts Tournament

binary search, brute force, greedy, math

The Winter Hike

constructive algorithms, greedy, math

Divan and Kostomuksha (easy version)

dp, number theory

Arena

combinatorics, dp, math

Treelabeling

bitmasks, constructive algorithms, dfs and similar, games, greedy, implementation, trees

Hidden Fortress

interactive, math

Staircases

brute force, combinatorics, data structures, dfs and similar, dp, implementation, math

Red-Black Number

dfs and similar, dp, implementation, math, meet-in-the-middle

Longest Array Deconstruction

data structures, divide and conquer, dp, sortings

Nearest Beautiful Number (hard version)

bitmasks, brute force, constructive algorithms, dfs and similar, dp, greedy

Boring Segments

data structures, sortings, trees, two pointers

Permutation Shift

brute force, combinatorics, constructive algorithms, dfs and similar, dsu, graphs, math

Domino (hard version)

constructive algorithms, implementation, math

How Many Paths?

dfs and similar, dp, graphs, trees

Gift Set

binary search, greedy, math, ternary search

Funny Substrings

data structures, hashing, implementation, matrices, strings

Minimax

constructive algorithms, greedy, strings

Assimilation IV

combinatorics, dp, math, probabilities, two pointers

Cut

binary search, data structures, dp, graphs, number theory, two pointers

Colorings and Dominoes

combinatorics, dp, greedy, math

Guide

Digits

dp, math, number theory

The Number of Pairs

dp, math, number theory

GCD of an Array

brute force, data structures, hashing, implementation, math, number theory, sortings, two pointers

Max Median

binary search, data structures, dp

Skyline Photo

data structures, divide and conquer, dp

Painting the Array II

constructive algorithms, data structures, dp, greedy, implementation

Moving to the Capital

dfs and similar, dp, graphs, shortest paths

New Year's Puzzle

brute force, dp, graph matchings, greedy, sortings

Euclid's nightmare

bitmasks, dfs and similar, dsu, graphs, greedy, math, sortings

Array Partition

binary search, data structures, greedy, two pointers

Errich-Tac-Toe (Easy Version)

constructive algorithms, math

Xor Tree

binary search, bitmasks, data structures, divide and conquer, dp, trees

Reducing Delivery Cost

brute force, graphs, shortest paths

Zero Remainder Sum

dp

Number Deletion Game

*special problem, dp, games, greedy

Neural Network Problem

*special problem, binary search, greedy