first commit.

Author: pinglu85

algorithms/pathfinding-algorithms/dijkstrasAlgorithm.js

@@ -0,0 +1,82 @@
+const PriorityQueue = require('../../data-structures/PriorityQueue');
+const Graph = require('../../data-structures/Graph');
+
+function dijkstrasAlgorithm(graph, source, target) {
+  const dijkstrasInfo = new Map();
+
+  graph.forEach((_, vertex) => {
+    const distanceToSource = vertex === source ? 0 : Infinity;
+    dijkstrasInfo.set(vertex, { distanceToSource, parent: null });
+  });
+
+  const pq = new PriorityQueue(
+    (vertexA, vertexB) => vertexA.distanceToSource - vertexB.distanceToSource
+  );
+
+  pq.insert({
+    vertex: source,
+    distanceToSource: 0,
+  });
+
+  const visited = new Set();
+
+  while (pq.size() > 0) {
+    const { vertex, distanceToSource } = pq.pull();
+
+    if (vertex === target) {
+      return constructPath(dijkstrasInfo, target);
+    }
+
+    if (visited.has(vertex)) {
+      continue;
+    }
+
+    visited.add(vertex);
+
+    const neighbors = graph.get(vertex).to;
+
+    neighbors.forEach((weight, neighbor) => {
+      if (visited.has(neighbor)) {
+        return;
+      }
+
+      const newDistanceToSource = distanceToSource + weight;
+      const oldDistanceToSource = dijkstrasInfo.get(neighbor).distanceToSource;
+
+      if (newDistanceToSource < oldDistanceToSource) {
+        dijkstrasInfo.set(neighbor, {
+          distanceToSource: newDistanceToSource,
+          parent: vertex,
+        });
+        pq.insert({ vertex: neighbor, distanceToSource: newDistanceToSource });
+      }
+    });
+  }
+
+  return [];
+}
+
+function constructPath(dijkstrasInfo, target) {
+  const path = [];
+  let vertex = target;
+
+  while (vertex) {
+    path.push(vertex);
+    const { parent } = dijkstrasInfo.get(vertex);
+    vertex = parent;
+  }
+
+  return path.reverse();
+}
+
+const graph = new Graph();
+graph.addEdge('A', 'B', 4);
+graph.addEdge('A', 'C', 7);
+graph.addEdge('B', 'C', 2);
+graph.addEdge('C', 'D', 3);
+graph.addEdge('C', 'F', 6);
+graph.addEdge('C', 'E', 1);
+graph.addEdge('D', 'F', 2);
+graph.addEdge('E', 'F', 3);
+const path = dijkstrasAlgorithm(graph.vertices, 'A', 'F');
+console.log(path);