min cut

Author: drewverlee

.gitignore

@@ -42,3 +42,4 @@ quick_sort_project/programming_question2.py
 quick_sort_project/solution.txt
 quick_sort_project/test.txt
 quick_sort_project/__pycache__
+min_cut_project/min_cut.py

min_cut_project/__init__.py

@@ -0,0 +1,21 @@
+"""
+       File : run.py
+     Author : Drew Verlee
+       Date : 16.07.13.
+      Email : drew.verlee@gmail.com
+     GitHub : https://github.com/Midnightcoffee/
+Description : putting it all together
+"""
+
+from tools import lowest, file_to_graph
+from min_cut import min_cut
+from copy import deepcopy
+
+def main(afile):
+    """ takes afile argument"""
+    G = file_to_graph(afile)
+    return min([min_cut(deepcopy(G)) for x in range(100)])
+
+
+if __name__ == '__main__':
+    print(main('kargerMinCut.txt'))

min_cut_project/kargerMinCut.txt

@@ -0,0 +1,58 @@
+file contains a list rep of a undirected graph
+200 vertices labled 1 to 200
+v  neighbors
+6  7 9 ... 
+
+run the randombized contradction algorithm for the min cut problem to compute
+the min cut.
+
+HINT!: figure out an implementation of the edge ontracitions.
+
+
+
+cut into two parts
+undirected
+set a     set b
+edge ---   edge
+edge --- edge 
+
+so above we have two cuts
+
+
+directed
+set a     set b
+edge --->   edge
+edge --- edge 
+now one cut
+
+
+min cut: fewest number of crossing edges. allow parallel edges - --- 
+ 
+
+random contraction algorithm:
+random sampling,
+
+
+input: undirected graph G = (v, e)
+parelle edges allowed
+
+return compute a cut wit the fewest number of crossing edges (a min cut)
+
+while there are more than 2 vertices:
+    pick a remaining edge (u, v) uniformaly at randombized
+    merge (or "contract") u and v into a single vertex
+    remove self-loops
+    return at represented by final 2 vertices
+
+items:
+have      need
+file need graph
+want a graph like {v :set([n, n]}
+
+then
+graph     min cut? 
+
+
+tools needed
+file_to_graph
+

min_cut_project/run.py

@@ -0,0 +1,8 @@
+1 2 3 4 7
+2 1 3 4
+3 1 2 4
+4 1 2 3 5
+5 4 6 7 8
+6 5 7 8
+7 1 5 6 8
+8 5 6 7

min_cut_project/sketch.txt

@@ -0,0 +1,4 @@
+1 2 3
+2 1 3 4
+3 1 2 4
+4 2 3

min_cut_project/tests/__init__.py

@@ -0,0 +1,33 @@
+"""
+       File : test_main.py
+     Author : Drew Verlee
+       Date : 16.07.13.
+      Email : drew.verlee@gmail.com
+     GitHub : https://github.com/Midnightcoffee/
+Description : TODO add description
+"""
+
+import unittest
+from min_cut_project.run import main
+
+class TestMain(unittest.TestCase):
+    """main tests"""
+
+
+    def test_one(self):
+        expected = 2
+        result = main('one.txt')
+        self.assertEqual(expected, result)
+
+    def test_two(self):
+        expected = 2
+        result = main('two.txt')
+        self.assertEqual(expected, result)
+
+    def test_three(self):
+        expected = 1
+        result = main('three.txt')
+        self.assertEqual(expected, result)
+
+if __name__ == '__main__':
+    unittest.main()

min_cut_project/tests/one.txt

@@ -0,0 +1,27 @@
+"""
+       File : test_min_cut.py
+     Author : Drew Verlee
+       Date : 16.07.13.
+      Email : drew.verlee@gmail.com
+     GitHub : https://github.com/Midnightcoffee/
+Description : test min cut
+"""
+
+import unittest
+from min_cut_project.min_cut import min_cut
+from min_cut_project.tools import file_to_graph
+
+class TestMinCut(unittest.TestCase):
+    """try to find the mind cut"""
+
+    def setUp(self):
+        a_file = 'test_data.txt'
+        self.G = file_to_graph(a_file)
+
+    def test_small_data(self):
+        expected = [2, 3]
+        returned = min_cut(self.G)
+        self.assertIn(returned, expected)
+
+if __name__ == '__main__':
+    unittest.main()