Created
September 26, 2013 01:50
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dijkstra
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'use strict'; | |
var assert = require('assert'); | |
var log = console.log; | |
// undirected graph | |
function Graph() { | |
this.nodes = []; | |
this.edges = {}; | |
this.dists = {}; | |
} | |
Graph.prototype = { | |
addNode: function (val) { | |
if (this.nodes.indexOf(val) == -1) return; | |
this.nodes.push(val); | |
}, | |
addEdge: function (from, to, dist) { | |
this._addEdge(from, to, dist); | |
this._addEdge(to, from, dist); | |
}, | |
_addEdge: function (from, to, dist) { | |
if (!this.edges[from]) this.edges[from] = []; | |
this.edges[from].push(to); | |
this.dists[[from, to]] = dist; | |
} | |
}; | |
var dijkstra = function (graph, start) { | |
// store visited node's distances | |
var dists = {}; | |
// Staring node distance | |
dists[start] = 0; | |
var path = {}; | |
var nodes = [].concat(graph.nodes); // make a copy so we don't kill graph | |
while (nodes.length) { | |
var min = null; | |
// Find smallest node remaining in graph | |
nodes.forEach(function (node) { | |
// node has been visited | |
if (dists[node] != null) { | |
// min not set or found smaller node | |
if (min == null || dists[node] < dists[min]) { | |
min = node; | |
} | |
} | |
}); | |
// no more nodes to look through | |
if (min == null) { | |
break; | |
} | |
// remove min node so we don't see it in our path anymore | |
var i = nodes.indexOf(min); | |
nodes.splice(i, 1); | |
var curDist = dists[min]; | |
// For each edge for the min node, find the shortest | |
// path to it's edges | |
graph.edges[min].forEach(function (edge) { | |
var dist = curDist + graph.dists[[min, edge]]; | |
// if edge found is shorter than a previously set edge | |
if (dists[edge] == null || dist < dists[edge]) { | |
dists[edge] = dist; | |
path[edge] = min; | |
} | |
}); | |
} // END WHILE | |
return path; | |
}; | |
var shortestPath = function (graph, start, end) { | |
var paths = dijkstra(graph, start); | |
var route = [end]; | |
if (Object.keys(paths).length < 2) return route; | |
// Traverse backwards through short path | |
while (end !== start) { | |
route.unshift(paths[end]); | |
end = paths[end]; | |
} | |
return route; | |
}; | |
var len = 7; | |
var vals = new Array(len); | |
for (var i = 0; i < len; i += 1) { | |
vals[i] = i + 1; | |
} | |
var g = new Graph(); | |
g.nodes = vals; | |
g.addEdge(1, 2, 7); | |
g.addEdge(1, 3, 9); | |
g.addEdge(1, 6, 14); | |
g.addEdge(2, 3, 10); | |
g.addEdge(2, 4, 15); | |
g.addEdge(3, 4, 11); | |
g.addEdge(3, 6, 2); | |
g.addEdge(4, 5, 6); | |
g.addEdge(5, 6, 9); | |
//log(g); | |
assert(shortestPath(g, 1, 5) + '' == [1, 3, 6, 5] + ''); | |
assert(shortestPath(g, 5, 1) + '' == [5, 6, 3, 1] + ''); | |
assert(shortestPath(g, 2, 5) + '' == [2, 3, 6, 5] + ''); | |
assert(shortestPath(g, 1, 4) + '' == [1, 3, 4] + ''); |
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