Problems
Automatic Input Verifier#1919
Very hard · Implementation
Friendly Points#1920
Easy · Geometry · Sorting · Binary Search
Expanding Lake#1921
Very hard · Geometry
Octahedron And Dominoes#1922
Easy · Dynamic programming
Tiny Puzzle#1923
Very hard · Brute force · Graphs
Circular Island#1924
Very hard · Geometry
Traffic Jam#1925
Very hard · Dynamic programming · Shortest paths
Number of Permutations#1926
Very easy · Dynamic programming · Math
Perspective#1927
Very easy · Graphs
Enjoy Arithmetic Progressions#1928
Very hard · Dynamic programming
Completely Non-zero Determinant#1929
Easy · Matrix
Fast Typing#1930
Very hard · Dynamic programming · Probabilities
XYZX 2009#1931
Very easy · Implementation
Greatest Greatest Common Divisor#1932
Very easy · Number theory
Colored Wizards - 2#1933
Very easy · Graphs
Graph of operations#1934
Very easy · 2-SAT
Regular matching#1935
Very hard · Graphs · Graph matchings
Flights#1936
Very easy · Graphs · Shortest paths
Fire safety#1937
Very easy · Graphs
Island Nations#1938
Easy · Graphs · Shortest paths
King#1939
Easy · Graphs
Ice rink#1940
Hard · Brute force · Implementation · Graphs · Depth-first Search
Ancestor#1941
Easy · Trees
Inevitability#1942
Very easy · Graphs
Bridges#1943
Very easy · Graphs