# HG changeset patch
# User Brian Neal <bgneal@gmail.com>
# Date 1354585226 21600
# Node ID 9f1fccc1399104b77687e57015edc8deab28926b
# Parent  1defe6fcf9d35d29b78786ba6ae0b346634f62f9
Added a program that does 2.3 exercise 6 (Paul Erdos).

diff -r 1defe6fcf9d3 -r 9f1fccc13991 ch2ex6.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ch2ex6.py	Mon Dec 03 19:40:26 2012 -0600
@@ -0,0 +1,55 @@
+"""ch2ex6.py - Program for Chapter 2.5, exercise 6.
+
+This program generates random graphs with parameters n and p and computes the
+fraction of them that are connected.
+
+"""
+import string
+
+from Graph import Vertex
+from RandomGraph import RandomGraph
+
+
+LABELS = string.letters + string.punctuation
+
+def test_graph(n, p):
+    """Generate a RandomGraph with parameters n & p and return True if the
+    graph is connected, False otherwise.
+
+    """
+    vs = [Vertex(c) for c in LABELS[:n]]
+    g = RandomGraph(vs)
+    g.add_random_edges(p)
+    return g.is_connected()
+
+
+def test_p(n, p, num):
+    """Generate num RandomGraphs with parameters n & p and return the number
+    of graphs that are connected.
+
+    """
+    count = 0
+    for i in range(num):
+        if test_graph(n, p):
+            count += 1
+
+    return count
+
+
+def main(script_name, n=26, p=0.1, num=1, *args):
+    """Generate num RandomGraphs with parameters n & p and print out the number
+    of graphs that are connected.
+
+    """
+
+    n = int(n)
+    p = float(p)
+    num = int(num)
+
+    count = test_p(n, p, num)
+    print count
+
+
+if __name__ == '__main__':
+    import sys
+    main(*sys.argv)