Simplified implementation of Minimum spanning tree using Kruskal’s Al…

…gorithm

README.md

@@ -2,7 +2,6 @@ Data structures
 ================
 [![Build Status](https://travis-ci.org/prawn-cake/data_structures.svg?branch=master)](https://travis-ci.org/prawn-cake/data_structures)
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-![PythonVersions](https://www.dropbox.com/s/ck0nc28ttga2pw9/python-2.7_3.4-blue.svg?dl=1)
 
 This is a pet project implementing different common and specific data structures in pure python.
 
@@ -28,6 +27,7 @@ my implementation is a good start to customize it for your needs.
 * [BK-Tree](https://en.wikipedia.org/wiki/BK-tree)
 * [Prefix tree](https://en.wikipedia.org/wiki/Trie)
 * [Disjoint set](https://en.wikipedia.org/wiki/Disjoint-set_data_structure)
+* [Minimum spannin tree](https://en.wikipedia.org/wiki/Minimum_spanning_tree)
 
 ## Links
 

structures/mst.py

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+"""Minimum spanning tree using Kruskal’s Algorithm"""
+
+from structures.disjoint_set import DSet
+
+
+if __name__ == '__main__':
+    # Format: (node P, node Q, distance)
+    # https://he-s3.s3.amazonaws.com/media/uploads/6322896.jpg
+    g = [
+        ('A', 'B', 1),
+        ('A', 'C', 7),
+
+        ('B', 'C', 5),
+        ('B', 'D', 4),
+        ('B', 'E', 3),
+
+        ('C', 'E', 6),
+        ('D', 'E', 2),
+    ]
+
+    dset = DSet(['A', 'B', 'C', 'D', 'E'])
+    mst = []
+    for p, q, distance in sorted(g, key=lambda item: item[2]):
+        print('--> %s' % ([p, q, distance]))
+        if dset.connected(p, q):
+            print('Cycle detected')
+            continue
+        dset.union(p, q)
+        mst.append((p, q, distance))
+
+    assert mst == [('A', 'B', 1), ('D', 'E', 2), ('B', 'E', 3), ('B', 'C', 5)]