public static string[] GetBuildOrder(string[] projects, string[,] dependencies)
{
//TODO: check cycles!
var graph = new Common.Graph <string, int>();
for (int i = 0; i < dependencies.GetUpperBound(0) + 1; i++)
{
graph.AddDirectedEdge(new Common.Edge <string, int>(dependencies[i, 0], dependencies[i, 1], 0));
}
var visited = new HashSet <string>();
var ordering = new string[projects.Length];
var indexOrdering = projects.Length - 1;
// find all non visited nodes with no connections to them
// and set them to return List, then mark them as visited
// in short, implement topological sort
foreach (var project in projects)
{
if (!visited.Contains(project))
{
// create list of visited nodes starting from 'project' node
var visitedNodes = new List <string>();
execDFS(project, visited, visitedNodes, graph);
foreach (var vn in visitedNodes)
{
ordering[indexOrdering] = vn;
indexOrdering = indexOrdering - 1;
}
}
}
return(ordering);
}
// Perform a depth first search on a graph with n nodes.
// This impl returns number of connected nodes starting from firstNode
public static int DFS(T[] nodes, Common.Edge <T, W>[] dependencies, T firstNode)
{
// Example
// nodes = { a, b, c, d, e, f }
// dependencies = { {a, d}, {f, b}, {b, d}, {f, a}, {d, c}}
// DFS(params, a).Count == 5 // connected to 5 other nodes
// DFS(params, e).Count == 1 // not connected to any other nodes
var graph = new Common.Graph <T, W>();
for (int i = 0; i < dependencies.Length; i++)
{
graph.AddDirectedEdge(dependencies[i]);
}
var numberOfNodes = nodes.Length;
// initialize visited list/map
var visited = new Dictionary <T, bool>();
foreach (var p in nodes)
{
visited[p] = false;
}
var count = 0;
// non recursive solution, here we use Stack
var stack = new pv.Common.Stack <T>(); // lets use homemade stack
stack.Push(firstNode);
visited[firstNode] = true;
while (!stack.IsEmpty())
{
var node = stack.Pop();
// famous doSomething :) e.g. count++
count++;
if (graph.ContainsKey(node))
{
foreach (var edge in graph[node])
{
if (!visited[edge.To])
{
stack.Push(edge.To);
visited[edge.To] = true;
}
}
}
}
return(count);
}
private static void execDFS(string project, HashSet <string> visited, List <string> visitedNodes, Common.Graph <string, int> graph)
{
visited.Add(project);
var edges = graph.ContainsKey(project) ? graph[project] : null;
if (edges != null)
{
foreach (var edge in edges)
{
if (!visited.Contains(edge.To))
{
execDFS(edge.To, visited, visitedNodes, graph);
}
}
}
visitedNodes.Add(project);
}