Heidi and Library (hard)

flows

Oleg and chess

data structures, divide and conquer, flows, graph matchings

ALT

data structures, flows, graphs, trees

Gosha is hunting

brute force, data structures, dp, flows, math, probabilities, sortings

Chess Championship

constructive algorithms, flows, greedy, math

Olympiad in Programming and Sports

dp, flows, graphs, greedy

T-shirts Distribution

constructive algorithms, flows, greedy

Goods transportation

dp, flows, greedy

One-Way Reform

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

Cactusophobia

dfs and similar, flows

Underfail

flows

Incorrect Flow

flows

Captain America

flows, greedy

Delivery Bears

binary search, flows, graphs

Bear and Fair Set

flows, graphs

New Year and Forgotten Tree

constructive algorithms, flows, graphs

Soldier and Traveling

flows, graphs, math

Scaygerboss

flows

Scaygerboss

flows

Fox And Dinner

flows

Array and Operations

flows, graph matchings, number theory

Deciphering

flows, graph matchings

Flow Optimality

constructive algorithms, flows, math

Nanami's Power Plant

flows

Petya and Pipes

flows, graphs, shortest paths

Pumping Stations

brute force, dfs and similar, divide and conquer, flows, graphs, greedy, trees

Ciel and Duel

dp, flows, greedy

Tidying Up

flows, graph matchings

Tidying Up

flows

Biologist

flows

k-Maximum Subsequence Sum

data structures, flows, graphs, implementation

Binary Tree on Plane

flows, trees

Flawed Flow

constructive algorithms, flows, graphs, greedy

Build String

flows, graphs

Planar Graph

flows, geometry, graphs

Privatization

flows, graphs

Machine Programming

flows, graphs

Bits of merry old England

flows, graphs

Pills

brute force, flows

Buying Sets

flows, graph matchings

Evacuation

flows, graphs, shortest paths

World Evil

dp, flows