#JS Graph Algorithms

This is partial code for learning about graph traversals. The file search.js is setup to use the sample data in slugraph.js, which is based on the adjacency list defined in graph.js.

Run

npm install

to make sure you have a local copy of the NPM Collections package for use in the queue in your Breadth-First Search solution.

For reference, traversal algorithms are given below. To turn these into valid JS, you'll need to add declarations and decide what it means to be visited or unvisited. Depending on your choices, you may not need to do the initializations at the beginning of the algorithm. The only catch is that the vertices in slugraph.js are numbered starting at 1, rather than 0.

For the purposes of playing around you can defined the functions process and processEdge to simply log out a message about visiting a vertex or edge.

For breadth-first search, there is a queue constructor in queue.js.

BFS(G, s) {
  for each vertex v in G {
    state[v] = unvisited;
    parent[v] = null;
  };

  state[s] = visited;
  queue.enqueue(s);

  while (queue not empty) {
    u = queue.dequeue();
    process(u);
    for each vertex v in neighbor(u) {
      processEdge(u,v);
      if (state[v] == unvisited) {
        state[v] == visited;
        parent[v] = u;
        queue.enqueue(v);
      }
    }
  }
}

For depth-first search, you can either replace the queue with a stack (changing enqueue to push, and dequeue to pop), or you can use the following recursive form:

DFS(G,u) {
  state[u] = visited;
  process(u);
  for each v in neighbors(u) {
    processEdge(u,v);
    if (state[v] == unvisited) {
      parent[v] = u;
      DFS(G,v);
    }
  }
}