LeetCode 787 Cheapest Flights Within K Stops - Problem Statement

You have $n$ cities connected by flights with costs. Find the cheapest route from city src to city dst with at most $k$ stops. A stop is an intermediate city between source and destination. This is a constrained shortest path problem. You cannot use standard Bellman-Ford because it finds paths with minimum edges, not constrained stops.

The constraint changes the relaxation logic. At most $k$ stops means at most $k+1$ flights (edges). You need to control how many edges are used in the shortest path.