Data commit

Task/Graph-colouring/11l/graph-colouring.11l

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+F first_avail_int(data)
+   ‘return lowest int 0... not in data’
+   V d = Set(data)
+   L(i) 0..
+      I i !C d
+         R i
+
+F greedy_colour(name, connections)
+   DefaultDict[Int, [Int]] graph
+
+   L(connection) connections.split(‘ ’)
+      I ‘-’ C connection
+         V (n1, n2) = connection.split(‘-’).map(Int)
+         graph[n1].append(n2)
+         graph[n2].append(n1)
+      E
+         graph[Int(connection)] = [Int]()
+
+   // Greedy colourisation algo
+   V order = sorted(graph.keys())
+   [Int = Int] colour
+   V neighbours = graph
+   L(node) order
+      V used_neighbour_colours = neighbours[node].filter(nbr -> nbr C @colour).map(nbr -> @colour[nbr])
+      colour[node] = first_avail_int(used_neighbour_colours)
+
+   print("\n"name)
+   V canonical_edges = Set[(Int, Int)]()
+   L(n1, neighbours) sorted(graph.items())
+      I !neighbours.empty
+         L(n2) neighbours
+            V edge = tuple_sorted((n1, n2))
+            I edge !C canonical_edges
+               print(‘       #.-#.: Colour: #., #.’.format(n1, n2, colour[n1], colour[n2]))
+               canonical_edges.add(edge)
+      E
+         print(‘         #.: Colour: #.’.format(n1, colour[n1]))
+   V lc = Set(colour.values()).len
+   print("    #Nodes: #.\n    #Edges: #.\n  #Colours: #.".format(colour.len, canonical_edges.len, lc))
+
+L(name, connections) [
+      (‘Ex1’, ‘0-1 1-2 2-0 3’),
+      (‘Ex2’, ‘1-6 1-7 1-8 2-5 2-7 2-8 3-5 3-6 3-8 4-5 4-6 4-7’),
+      (‘Ex3’, ‘1-4 1-6 1-8 3-2 3-6 3-8 5-2 5-4 5-8 7-2 7-4 7-6’),
+      (‘Ex4’, ‘1-6 7-1 8-1 5-2 2-7 2-8 3-5 6-3 3-8 4-5 4-6 4-7’)]
+   greedy_colour(name, connections)