gca/BFS/index.js

Use classic algorithms for Graphs.

const bfsGraph = require("./BFS-Graph");

/**
 * BFS algorithm.
 * @param {Graph} graph The given graph for BFS
 * @param {number} s ID of root node.
 * @returns {bfsGraph} BFS graph. Return null if there no such s node in the original graph.
 */
function BFS(graph, s) {
  if (!graph.hasNode(s)) return null;

  const bfsG = new bfsGraph();
  const explored = new Set();

  bfsG.addNode(s);
  bfsG.addLayer();
  bfsG.addNodeToLayer(s, 0);
  explored.add(s);

  let numberOfNodesInLayer = bfsG.layerSize(bfsG.layersNumber() - 1);
  while (numberOfNodesInLayer > 0) {
    bfsG.addLayer();

    const parents = bfsG.getNodesFromLayer(bfsG.layersNumber() - 2);

    for (const parent of parents) {
      const children = graph.getNodesOfEdgesStartingNode(parent);
      const childrenNotExplored = children.filter(node => !explored.has(node));
      const childrenNotExploredIterator = childrenNotExplored.values();

      for (const child of childrenNotExploredIterator) {
        bfsG.addNode(child);
        bfsG.addEdge(parent, child);
        bfsG.addNodeToLayer(child, bfsG.layersNumber() - 1);
        explored.add(child);
      }
    }

    numberOfNodesInLayer = bfsG.layerSize(bfsG.layersNumber() - 1);
  }

  bfsG.layers.pop();
  return bfsG;
}

module.exports = BFS;