Problems

Very easy · Graphs · Implementation

Very hard · Brute force · String suffix structures

Very hard · Geometry

Very easy · Math

Very hard · Graphs · Dynamic programming

Very easy · Implementation

Easy · Prime factorization · Binary Search

Medium · Dynamic programming

Very hard · Geometry

Easy · Graphs · Shortest paths

Medium · Greedy algorithms · Sorting · Disjoint set union · Graphs

Hard · Breadth-first Search · Shortest paths · Graphs

Easy · Implementation

Very hard · Geometry

Very hard · Math · Number theory · Combinatorics · Matrix · Constructive Algorithms

Hard · Breadth-first Search · Bitmasks · Graphs

Medium · Geometry

Very hard · Dynamic programming · Bitmasks

Very hard · Trees · Data Structures · Range queries · Dynamic programming

Very easy · Graphs · Dynamic programming

Easy · Dynamic programming · Combinatorics

Medium · Dynamic programming · Binary Search

Easy · Graphs · Geometry

Medium · Math · Dynamic programming

Hard · Greedy algorithms · Trees · Sorting · Breadth-first Search