Problems
Fifteen Puzzle#3669
Very hard · Graphs
Polygon Game#3670
Very hard · Games
Checking for a Subsequence#3671
Very hard · Strings
Divisors of 2#3672
Easy · Number theory · Math · Prime factorization
Obtuse Angle Decomposition#3673
Hard · Constructive Algorithms · Math
Accordion#3674
Easy · Brute force
Chain#3675
Very hard · Combinatorics · Number theory · Math
Matrix#3677
Hard · Binary Search
Mandatory vertices#3678
Very hard · Graphs
Permutation logarithm#3679
Hard · Brute force
Tree Isomorphism#3680
Easy · Graphs · Depth-first Search
Filling the matrix in a spiral#3681
Very easy · Implementation
Fire in the Country#3682
Very easy · Games
Triangle and Circle#3683
Very hard · Geometry
Report 1#3684
Very hard · Binary Search · Combinatorics · Number theory
Report 3#3685
Very hard · Number theory · Math
How many are good?#3686
Medium · Dynamic programming · Combinatorics
Proto P#3687
Very easy · Math
Simple coincidence#3688
Hard · Dynamic programming · Number theory · Combinatorics · Math
Snake#3689
Very hard · Dynamic programming
Fingers#3690
Easy · Graphs · Games
Simple Monotony#3691
Very easy · Graphs · Greedy algorithms
Reverse Averaging#3692
Very hard · Implementation
Determinant#3693
Hard · Matrix
Exercise#3694
Easy · Math