LeetCode 787 Cheapest Flights Within K Stops - Implementation

Here is the solution:

dist := [inf] * n
dist[src] := 0
for round from 1 to k + 1
    prev := copy of dist
    for (u, v, w) in edges
        if prev[u] + w < dist[v] then
            dist[v] := prev[u] + w
return dist[dst] if dist[dst] != inf else -1

Copying $dist$ to prev at the start of each iteration keeps layers separate. Reading from prev and writing to $dist$ ensures each iteration represents exactly one additional edge.

This runs in $O(VE)$ time and uses $O(V)$ space.