Day 21 — Shortest Paths

What you’ll learn here

• BFS — the simplest shortest-path algorithm, perfect for unweighted graphs
• Dijkstra’s algorithm — O((V + E) log V) with a priority queue, for non-negative weights
• Bellman-Ford — slower (O(V·E)) but handles negative edge weights and detects negative cycles
• Floyd-Warshall — all-pairs shortest paths in O(V³), great for dense graphs

Picking the right algorithm depends on the graph: which weights, how dense, do you need one path or all of them.