Problems
Sphere#1969
Very hard · Graphs · Shortest paths
David Copperfield is resting#1970
Very easy · Implementation
Fateful Chess Puzzle#1971
Very easy · Combinatorics
Splitting#1972
Medium · Number theory
Rollback#1973
Very easy · Segment Tree · Prefix Sums · Queries
Random Acts of Kindness Day#1974
Very easy · Math · Implementation
The tightly bound son of the mountains#1975
Hard · Graphs · Shortest paths
Programming is an art!#1976
Very hard · Greedy algorithms
Well, a very common method for graphs...#1977
Easy · Graphs
Organizational Problems: A Topic for a Dissertation?#1978
Easy · Graphs · Graph network flows
Railroad#1979
Medium · Graphs · Depth-first Search · Graph matchings
Shadow Protocol#1980
Very easy · Chinese remainder theorem
Mushroom#1981
Very easy · Dynamic programming
Highways#1982
Medium · Graphs
Ricefield#1983
Very easy · Implementation
Fractions#1984
Easy · Math · Combinatorics
Primes Anna#1985
Medium · Number theory · Implementation
Anna and the palindrome#1986
Medium · Strings · Brute force
The Next Permutation#1987
Very easy · Implementation
The largest increasing subsequence#1988
Easy · Dynamic programming
Maximum matching#1989
Medium · Graph matchings · Graphs · Breadth-first Search · Depth-first Search
Domino 2#1990
Very easy · Graphs
Maximum flow#1991
Very easy · Graphs
Dividing the graph#1992
Easy · Graphs
Weighing#1993
Very easy · Math