Phase 2 / sliding-window, inclusion-exclusion
Phase 5 / prefix_sum/divisor/unique
Phase 4 / greedy/flipping/min_cost
Phase 5 / greedy/xor/array_manipulation
Phase 6 / prefix-sum/partition
Phase 6 / sliding-window/set
Phase 6 / prefix-sum/queries
Phase 6 / gcd/sliding-window
Phase 6 / greedy/xor
Phase 6 / greedy/array
Phase 4 / bfs, array, shortest path
Phase 4 / greedy, math, optimization