modify Dijkstra's algorithm to compute shortest path only for the vertex which is no more than three edges away from the start vertex

Question

i want to modify Dijkstra algorithm to compute shortest path only for the vertex which is no more than three edges away from the start vertex

I tried it with BFS(breadth first search). Initially calculates the number of edges away from source to each vertex v. Then run Dijkstra's algorithm with a constraint like relaxation u if and only if edges size from the source to u is no longer than three. Is it correct or Are there another method to find it.(using Dijkstra algorithm)

Answer 1

What if we add a simple if condition to check the parents since the number of parents to check is less (i.e. 3)?

In the dijkstra's algorithm,

  Dijkstra(G,W,s)
       Initialize_Single_Source(G,s)
       S= {}
       Q = V[G]
       while Q != {} do
          u = extract_min(Q)
          S = S U {u}
          for each vertex v element of Adj[u] do
                if(parent[u]==NIL || parent[u]==s || parent[parent[u]]==s)
                     relax(u,v,w)

Answer 2

I assume you want to only calculate shortest paths, starting from $s$, to vertices in its 3-hop neighborhood, i.e. vertices which are reachable from the start vertex $s$ with a path length $\leq 3$.

Use a limited breadth-first search and save the frontier vertices in a queue which is sorted according to its edge-weights. By doing that you have a priority queue and can update vertices like in the regular Dijkstra's algorithm. Note that you need to keep track of the current depth of the breadth-first search.