chapter 9 - shortest path algorithms

loiane · loiane · commit 433e4c0644f7 · 2016-03-06T15:39:50.000-03:00
diff --git a/chapter09/03-ShortestPath.js b/chapter09/03-ShortestPath.js
@@ -0,0 +1,85 @@
+function ShortestPath(graph) {
+
+  this.graph = graph;
+
+  var INF = Number.MAX_SAFE_INTEGER;
+
+  var minDistance = function(dist, visited){
+
+        var min = INF,
+            minIndex = -1;
+
+        for (var v = 0; v < dist.length; v++){
+            if (visited[v] == false && dist[v] <= min){
+                min = dist[v];
+                minIndex = v;
+            }
+        }
+
+        return minIndex;
+    };
+
+    this.dijkstra = function(src){
+
+        var dist = [],
+            visited = [],
+            length = this.graph.length;
+
+        // Initialize all distances as INFINITE (JavaScript max number) and visited[] as false
+        for (var i = 0; i < length; i++) {
+            dist[i] = INF;
+            visited[i] = false;
+        }
+
+        // Distance of source vertex from itself is always 0
+        dist[src] = 0;
+
+        // Find shortest path for all vertices
+        for (var i = 0; i < length-1; i++){
+
+            // Pick the minimum distance vertex from the set of vertices
+            // not yet processed. u is always equal to src in first
+            // iteration.
+            var u = minDistance(dist, visited);
+
+            // Mark the picked vertex as processed
+            visited[u] = true;
+
+            // Update dist value of the adjacent vertices of the
+            // picked vertex.
+            for (var v = 0; v < length; v++){
+                if (!visited[v] && this.graph[u][v]!=0 && dist[u] != INF && dist[u]+this.graph[u][v] < dist[v]){
+                    dist[v] = dist[u] + this.graph[u][v];
+                }
+            }
+        }
+
+        return dist;
+    };
+
+    this.floydWarshall = function(){
+
+        var dist = [],
+            length = this.graph.length,
+            i, j, k;
+
+        for (i = 0; i < length; i++){
+            dist[i] = [];
+            for (j = 0; j < length; j++){
+                dist[i][j] = this.graph[i][j];
+            }
+        }
+
+        for (k = 0; k < length; k++){
+            for (i = 0; i < length; i++){
+                for (j = 0; j < length; j++){
+                    if (dist[i][k] + dist[k][j] < dist[i][j]){
+                        dist[i][j] = dist[i][k] + dist[k][j];
+                    }
+                }
+            }
+        }
+
+        return dist;
+    }
+}
diff --git a/chapter09/04-UsingShortestPathAlgorithms.html b/chapter09/04-UsingShortestPathAlgorithms.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title></title>
+</head>
+<body>
+<script src="03-ShortestPath.js"></script>
+<script src="04-UsingShortestPathAlgorithms.js"></script>
+</body>
+</html>
diff --git a/chapter09/04-UsingShortestPathAlgorithms.js b/chapter09/04-UsingShortestPathAlgorithms.js
@@ -0,0 +1,43 @@
+//adjacent matrix
+var graph = [[0, 2, 4, 0, 0, 0],
+             [0, 0, 1, 4, 2, 0],
+             [0, 0, 0, 0, 3, 0],
+             [0, 0, 0, 0, 0, 2],
+             [0, 0, 0, 3, 0, 2],
+             [0, 0, 0, 0, 0, 0]];            
+
+var shortestPath = new ShortestPath(graph);
+
+console.log("********* Dijkstra's Algorithm - Shortest Path ***********");
+
+var dist = shortestPath.dijkstra(0);
+
+for (var i = 0; i < dist.length; i++){
+    console.log(i + '\t\t' + dist[i]);
+}
+
+console.log("********* Floyd-Warshall Algorithm - All-Pairs Shortest Path ***********");
+
+var INF = Number.MAX_SAFE_INTEGER;
+graph = [[0, 2, 4, INF, INF, INF],
+        [INF, 0, 1, 4, 2, INF],
+        [INF, INF, 0, INF, 3, INF],
+        [INF, INF, INF, 0, INF, 2],
+        [INF, INF, INF, 3, 0, 2],
+        [INF, INF, INF, INF, INF, 0]];
+
+shortestPath = new ShortestPath(graph);
+
+dist = shortestPath.floydWarshall();
+
+var s = '';
+for (var i=0; i<dist.length; ++i) {
+    s = '';
+    for (var j=0; j<dist.length; ++j) {
+        if (dist[i][j] === INF)
+            s += "INF ";
+        else
+            s += dist[i][j]+"   ";
+    }
+    console.log(s);
+}
