How many trees?

combinatorics, divide and conquer, dp

Hexadecimal's Numbers

brute force, implementation, math

Running Student

brute force, geometry, implementation

Die Roll

math, probabilities

Beads

dp, graphs

Two Friends

binary search, geometry

Looking for Order

bitmasks, dp

Obsession with Robots

constructive algorithms, graphs, implementation

Train and Peter

strings

Defining Macros

dp, expression parsing, implementation

Palindrome Degree

hashing, strings

Line

math, number theory

Memory Manager

implementation

Kalevitch and Chess

brute force, constructive algorithms

Exposition

binary search, data structures, dsu, trees, two pointers

Lizards and Basements 2

brute force, dp

Alice, Bob and Chocolate

greedy, two pointers

President's Office

implementation

Triangle

brute force, geometry

Bindian Signalizing

data structures

Follow Traffic Rules

implementation, math

Longest Regular Bracket Sequence

constructive algorithms, data structures, dp, greedy, sortings, strings

Center Alignment

implementation, strings

Chat Servers Outgoing Traffic

implementation

Mysterious Present

dp, sortings

Registration System

data structures, hashing, implementation

Before an Exam

constructive algorithms, greedy

Watermelon

brute force, math

Least Cost Bracket Sequence

greedy

Tic-tac-toe

brute force, games, implementation

Lorry

greedy, sortings

Shortest path of the king

greedy, shortest paths

Commentator problem

geometry

The least round way

dp, math

Winner

hashing, implementation

Ancient Berland Circus

geometry, math

Spreadsheet

implementation, math

Theatre Square

math