Dijkstra Smallest Path

maths/DijkstraSmallestPath.js

@@ -0,0 +1,102 @@
+function solve(graph, s) {
+  var solution = {};
+  solutions[s] = [];
+  solutions[s].dist = 0;
+  
+  while(true) {
+    var parent = null;
+    var nearest = null;
+    var dist = Infinity;
+    
+
+    for(var n in solutions) {
+      if(!solutions[n])
+        continue
+      var ndist = solutions[n].dist;
+      var adj = graph[n];
+      //for each of its adjacent nodes...
+      for(var a in adj) {
+        //without a solution already...
+        if(solutions[a])
+          continue;
+        //choose nearest node with lowest *total* cost
+        var d = adj[a] + ndist;
+        if(d < dist) {
+          //reference parent
+          parent = solutions[n];
+          nearest = a;
+          dist = d;
+        }
+      }
+    }
+    
+
+    if(dist === Infinity) {
+        break;
+    }
+
+    solutions[nearest] = parent.concat(nearest);
+
+    solutions[nearest].dist = dist;
+  }
+  
+  return solutions;
+}
+
+var graph = {};
+
+\\create graph
+
+var layout = {
+  'R': ['2'],
+  '2': ['3','4'],
+  '3': ['4','6','13'],
+  '4': ['5','8'],
+  '5': ['7','11'],
+  '6': ['13','15'],
+  '7': ['10'],
+  '8': ['11','13'],
+  '9': ['14'],
+  '10': [],
+  '11': ['12'],
+  '12': [],
+  '13': ['14'],
+  '14': [],
+  '15': []
+}
+
+//convert uni-directional to bi-directional graph
+// needs to look like: where: { a: { b: cost of a->b }
+// var graph = {
+//     a: {e:1, b:1, g:3},
+//     b: {a:1, c:1},
+//     c: {b:1, d:1},
+//     d: {c:1, e:1},
+//     e: {d:1, a:1},
+//     f: {g:1, h:1},
+//     g: {a:3, f:1},
+//     h: {f:1}
+// };
+
+for(var id in layout) {
+  if(!graph[id])
+    graph[id] = {};
+  layout[id].forEach(function(aid) {
+    graph[id][aid] = 1;
+    if(!graph[aid])
+      graph[aid] = {};
+    graph[aid][id] = 1;
+  });
+}
+
+//choose start node
+var start = '10';
+//get all solutions
+var solutions = solve(graph, start);
+
+console.log("From '"+start+"' to");
+//display solutions
+for(var s in solutions) {
+  if(!solutions[s]) continue;
+  console.log(" -> " + s + ": [" + solutions[s].join(", ") + "]   (dist:" + solutions[s].dist + ")");
+}