dist-javascript-algorithms-and-data-structures/dist/algorithms/graph/topological-sorting/topologicalSort.js

Algorithms and data-structures implemented on JavaScript

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = topologicalSort;

var _Stack = _interopRequireDefault(require("../../../data-structures/stack/Stack"));

var _depthFirstSearch = _interopRequireDefault(require("../depth-first-search/depthFirstSearch"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * @param {Graph} graph
 */
function topologicalSort(graph) {
  // Create a set of all vertices we want to visit.
  const unvisitedSet = {};
  graph.getAllVertices().forEach(vertex => {
    unvisitedSet[vertex.getKey()] = vertex;
  }); // Create a set for all vertices that we've already visited.

  const visitedSet = {}; // Create a stack of already ordered vertices.

  const sortedStack = new _Stack.default();
  const dfsCallbacks = {
    enterVertex: ({
      currentVertex
    }) => {
      // Add vertex to visited set in case if all its children has been explored.
      visitedSet[currentVertex.getKey()] = currentVertex; // Remove this vertex from unvisited set.

      delete unvisitedSet[currentVertex.getKey()];
    },
    leaveVertex: ({
      currentVertex
    }) => {
      // If the vertex has been totally explored then we may push it to stack.
      sortedStack.push(currentVertex);
    },
    allowTraversal: ({
      nextVertex
    }) => {
      return !visitedSet[nextVertex.getKey()];
    }
  }; // Let's go and do DFS for all unvisited nodes.

  while (Object.keys(unvisitedSet).length) {
    const currentVertexKey = Object.keys(unvisitedSet)[0];
    const currentVertex = unvisitedSet[currentVertexKey]; // Do DFS for current node.

    (0, _depthFirstSearch.default)(graph, currentVertex, dfsCallbacks);
  }

  return sortedStack.toArray();
}