XORificator

bitmasks, brute force, greedy, hashing

Nikita and LCM

brute force, data structures, dp, greedy, math, number theory, sortings

Binary Colouring

bitmasks, constructive algorithms, greedy, math

Little Nikita

math

Remove Bridges

data structures, dfs and similar, dp, greedy, sortings, trees

Splittable Permutations

combinatorics, data structures, dfs and similar, greedy, math, trees

Invertible Bracket Sequences

binary search, combinatorics, data structures, divide and conquer, implementation, two pointers

Job Interview

binary search, dp, greedy, implementation, two pointers

Increase/Decrease/Copy

greedy, implementation

Verify Password

implementation, sortings, strings

Mind Bloom

dp

378QAQ and Core

greedy, strings

Zimpha Fan Club

fft, greedy, math, strings

Set

bitmasks, brute force, combinatorics, dfs and similar, divide and conquer, dp, math

Chain Queries

binary search, data structures, dfs and similar, implementation, trees

Paint the Tree

brute force, dfs and similar, dp, greedy, shortest paths, trees

Chamo and Mocha's Array

binary search, brute force, greedy

378QAQ and Mocha's Array

brute force, greedy, math, sortings

Bazoka and Mocha's Array

brute force, greedy, implementation, sortings

Money Buys Less Happiness Now

data structures, greedy, sortings

Cutting Game

binary search, brute force, data structures, implementation, sortings, two pointers

Money Buys Happiness

dp

Ingenuity-2

constructive algorithms, greedy, implementation

Beautiful Triple Pairs

combinatorics, data structures

Symmetric Encoding

implementation, sortings, strings

Phone Desktop

greedy, math

Maximum GCD Sum Queries

bitmasks, brute force, dp, implementation, number theory

Cat, Fox and Swaps

graphs, math, sortings

Cat, Fox and Maximum Array Split

brute force, interactive, math

Cat, Fox and Double Maximum

constructive algorithms, greedy, implementation, math, sortings

Cat, Fox and the Lonely Array

binary search, bitmasks, data structures, greedy, math, two pointers

Chess For Three

brute force, dp, implementation, math

Coin Games

games

Contest Proposal

brute force, greedy, two pointers

±1

2-sat, dfs and similar, graphs

XOUR

data structures, dsu, sortings

Circle Perimeter

binary search, brute force, dfs and similar, geometry, implementation, math

Find the Car

binary search, math, sortings

Binary Cut

dp, greedy, implementation, sortings, strings

Clock and Strings

implementation

Different String

implementation, strings

My First Sorting Problem

implementation, sortings

Min-Fund Prison (Hard)

bitmasks, dfs and similar, dp, graphs, trees

Min-Fund Prison (Medium)

brute force, dfs and similar, dp, graphs, trees

Min-Fund Prison (Easy)

dfs and similar, trees

Playing Quidditch (Hard)

implementation

Playing Quidditch (Medium)

implementation

Playing Quidditch (Easy)

implementation

Trails (Hard)

dp, matrices

Trails (Medium)

dp, matrices

Trails (Easy)

dp

Arithmancy (Hard)

interactive

Arithmancy (Medium)

constructive algorithms, interactive, probabilities, strings

Arithmancy (Easy)

brute force, constructive algorithms, interactive, strings

Game on Tree (Hard)

dfs and similar, dp, games, trees

Game on Tree (Medium)

dfs and similar, dp, games, trees

Game on Tree (Easy)

games

Exact Neighbours (Hard)

constructive algorithms

Exact Neighbours (Medium)

constructive algorithms

Exact Neighbours (Easy)

constructive algorithms

Balanced Unshuffle (Hard)

constructive algorithms, trees

Balanced Unshuffle (Medium)

brute force, constructive algorithms, trees

Balanced Shuffle (Easy)

implementation, sortings

Card Pairing

dp, greedy, hashing, implementation

Unique Array

binary search, data structures, divide and conquer, dp, greedy

Shop Game

data structures, greedy, math, sortings

Minimizing the Sum

dp, implementation

Shifts and Sorting

constructive algorithms, greedy

Two Friends

constructive algorithms, implementation, math

Division + LCP (hard version)

binary search, brute force, data structures, dp, hashing, math, string suffix structures, strings

Division + LCP (easy version)

binary search, data structures, dp, hashing, string suffix structures, strings

Equal XOR Segments

binary search, data structures

Cells Arrangement

constructive algorithms

Permutation Game

brute force, dfs and similar, games, graphs, greedy, math

Assembly via Remainders

constructive algorithms, number theory

Prefiquence

greedy, two pointers

Maximize?

brute force, math, number theory

Next and Prev

brute force, data structures, implementation

Again Counting Arrays (Hard Version)

combinatorics, dp, math

Again Counting Arrays (Easy Version)

combinatorics, dp, fft, math

Long Way to be Non-decreasing

binary search, dfs and similar, graphs, implementation, shortest paths, two pointers

Fenwick Tree

bitmasks, brute force, combinatorics, data structures, dp, math, trees

Reverse Card (Hard Version)

brute force, math, number theory

Reverse Card (Easy Version)

brute force, math, number theory

Permutation Counting

binary search, greedy, implementation, math, sortings

Rectangle Filling

constructive algorithms, implementation

Card Exchange

constructive algorithms, games, greedy

Conference

data structures, flows

Connected Cubes

constructive algorithms, games

Missing Subarray Sum

constructive algorithms

Folding Strip

constructive algorithms, greedy, strings

Missing Subsequence Sum

bitmasks, constructive algorithms, greedy, number theory

Everything Nim

games, greedy, math, sortings

Necromancer

*special problem

Equal Trees

*special problem, graphs, meet-in-the-middle

Composite Spells

*special problem, dp

Observation Towers

*special problem

Narrow Paths

*special problem, combinatorics

Yet Another Permutation Constructive

*special problem, constructive algorithms

Staircase

*special problem