There are `n` cities and `flights` where flights[i] = [from, to, price]. Return the cheapest price to go from `src` to `dst` using at most `k` stops (at most k intermediate cities), or -1 if there is no such route.
Examples
in: n = 4, flights = [[0,1,100],[1,2,100],[2,0,100],[1,3,600],[2,3,200]], src = 0, dst = 3, k = 1