I Love Balls

combinatorics, math, probabilities

Swap Dilemma

constructive algorithms, data structures, divide and conquer, greedy, math, sortings

Sorting Problem Again

binary search, data structures, sortings

Number of k-good subarrays

bitmasks, brute force, combinatorics, divide and conquer, dp, math, meet-in-the-middle

Beauty of the mountains

brute force, data structures, implementation, math, number theory

Turtle and Paths on a Tree

data structures, dp, trees

Turtle and Intersected Segments

data structures, dsu, graphs, greedy

Turtle and Multiplication

constructive algorithms, dfs and similar, graphs, number theory

Turtle and an Incomplete Sequence

bitmasks, brute force, constructive algorithms, greedy, implementation, math

Yasya and the Mysterious Tree

bitmasks, data structures, dfs and similar, graphs, greedy, strings, trees

Field Division (hard version)

math, sortings

Field Division (easy version)

data structures, math, sortings

Permutation of Rows and Columns

constructive algorithms, data structures, greedy, hashing, implementation, math, matrices, sortings

Kostyanych's Theorem

brute force, constructive algorithms, graphs, interactive

Manhattan Triangle

binary search, constructive algorithms, data structures, geometry, implementation, two pointers

Fixing a Binary String

bitmasks, brute force, constructive algorithms, dp, greedy, hashing, strings

Large Graph

data structures, dfs and similar, dsu, graphs, number theory, two pointers

Computing Machine

brute force, data structures, dp, greedy, implementation

Elections

data structures, greedy, implementation, math

Tensor

constructive algorithms, graphs, interactive

XORificator

bitmasks, brute force, greedy, hashing

Nikita and LCM

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

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

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

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

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

±1

2-sat, dfs and similar, graphs

XOUR

data structures, dsu, sortings

Circle Perimeter

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

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

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

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

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

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

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

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

Frequency Mismatch (Hard Version)

binary search, data structures, dfs and similar, hashing, probabilities, trees

Frequency Mismatch (Easy Version)

binary search, data structures, divide and conquer, hashing, probabilities, trees

Carousel of Combinations

brute force, combinatorics, dp, math, number theory

A BIT of an Inequality

bitmasks, brute force, dp, math

How Does the Rook Move?

combinatorics, dp, math

Nene and the Passing Game

constructive algorithms, data structures, dsu, graphs, sortings

Nene vs. Monsters (Hard Version)

brute force, greedy, implementation, math

Nene vs. Monsters (Easy Version)

brute force, implementation, math

Nene and the Mex Operator

bitmasks, brute force, constructive algorithms, divide and conquer, dp, greedy, implementation, math

Nene's Magical Matrix

constructive algorithms, greedy, math

The Most Reckless Defense

bitmasks, brute force, constructive algorithms, dp, flows, graph matchings, shortest paths

GCD on a grid

brute force, dfs and similar, dp, implementation, math, number theory

Unfair Game

dp, games, greedy, math, schedules