Problems
Brackets#1994
Easy · Data Structures
How can I help?#1995
Very hard · Dynamic programming
Cupcakes#1996
Easy · Math
Approaching by progression#1997
Very easy · Math
Tori#1998
Easy · Geometry
Palindrome#1999
Hard · Strings
Minefield#2000
Hard · Greedy algorithms
Device Survey#2001
Very easy · Binary Search · Graphs
Pattern Coloring#2002
Easy · Sorting · Prefix Sums
Cellular communication#2003
Hard · Graphs · Brute force
Routing#2004
Very hard · Binary Search
Weighing 2#2005
Very hard · Brute force · Combinatorics · Dynamic programming · Implementation · Graphs
Plus and xor#2006
Easy · Bitmasks
Gift#2007
Medium · Graphs · Greedy algorithms
Tourist#2008
Medium · Binary Search
Points#2009
Easy · Math
Mice and Cheese#2010
Easy · Greedy algorithms · Sorting
Mutation#2011
Medium · Dynamic programming · Implementation
Sequence#2012
Very easy · Dynamic programming
Area of the hexagon#2013
Very easy · Geometry
Lucky Number#2014
Very easy · Implementation
Game XOR#2015
Hard · Games · Math · Combinatorics
Determinant of the matrix#2017
Easy · Matrix
Minimal d-exponent#2018
Medium · Number theory · Brute force
Fibonacci sequence#2019
Medium · Hashing · Dynamic programming