Merge pull request #69 from krm35/feature/shortestPaths

Add a shortestPaths function

Author: curran

src/index.ts

@@ -33,6 +33,7 @@ export function Graph(serialized?: Serialized) {
     lowestCommonAncestors,
     topologicalSort,
     shortestPath,
+    shortestPaths,
     serialize,
     deserialize,
   };
@@ -390,6 +391,30 @@ export function Graph(serialized?: Serialized) {
     return path();
   }
 
+  function shortestPaths(source: NodeId, destination: NodeId) {
+    let path = shortestPath(source, destination);
+    const paths = [path],
+        removedEdges = [],
+        weight = path.weight;
+    while (weight) {
+      removeEdge(path[0], path[1]);
+      removeEdge(path[1], path[0]);
+      removedEdges.push([path[0], path[1]]);
+      try {
+        path = shortestPath(source, destination);
+        if (!path.weight || weight < path.weight) break;
+        paths.push(path);
+      } catch (e) {
+        break;
+      }
+    }
+    for (const [u, v] of removedEdges) {
+      addEdge(u, v);
+      addEdge(v, u);
+    }
+    return paths;
+  }
+
   // Serializes the graph.
   function serialize() {
     const serialized: Serialized = {

test.js

@@ -426,6 +426,25 @@ describe("Graph", function () {
         withWeight(["a", "b", "c"], 2)
       );
     });
+
+    it("Should compute shortest paths on six edges.", function () {
+      var graph = Graph()
+          .addEdge("a", "b")
+          .addEdge("b", "c")
+          .addEdge("a", "d")
+          .addEdge("d", "c")
+          .addEdge("a", "e")
+          .addEdge("e", "f")
+          .addEdge("f", "c");
+      assert.deepEqual(graph.shortestPaths("a", "c"), [
+        withWeight(["a", "b", "c"], 2),
+        withWeight(["a", "d", "c"], 2),
+      ]);
+      // need to check nodes are still present because we remove them to get all shortest paths
+      const nodes = ["a", "b", "c", "d", "e", "f"];
+      assert.equal(graph.nodes().length, nodes.length);
+      nodes.forEach((node) => assert(contains(graph.nodes(), node)));
+    });
   });
 
   describe("hadEdge", function () {