From 085b59d339e89b851766382c3761597586f4f3f6 Mon Sep 17 00:00:00 2001
From: Eric Anderson <ejona86@gmail.com>
Date: Sat, 2 Oct 2010 00:58:36 -0500
Subject: Completely change implementation

---
 finder.py | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 89 insertions(+), 16 deletions(-)
 mode change 100644 => 100755 finder.py

(limited to 'finder.py')

diff --git a/finder.py b/finder.py
old mode 100644
new mode 100755
index 0a5fff3..1e5d930
--- a/finder.py
+++ b/finder.py
@@ -1,21 +1,94 @@
+#!/usr/bin/env python
 import sys
+import cPickle
+import heapq
+import string
+chars = string.lowercase
 
-def find_transformations(input_word, output_word, graph):
-    seen = set([input_word])
-    queue = [(input_word, ())]
-    while queue:
-        (i, parents) = queue.pop(0)
-        can_make = [j for j in graph[i] if j not in seen]
-        if output_word in can_make:
-            print ' '.join(parents), output_word
-            return True
-        new_parents = parents + (i,)
-        queue.extend([(w, new_parents) for w in can_make])
-        for w in can_make: seen.add(w)
-    return False
+def flub(word, wordlist):
+    for i in range(len(word)):
+        for c in chars:
+            new_word = word[:i] + c + word[i+1:]
+            if new_word != word and new_word in wordlist:
+                yield new_word
+
+def hamming_distance(s1, s2):
+    assert len(s1) == len(s2)
+    return sum(ch1 != ch2 for ch1, ch2 in zip(s1, s2))
+
+class Graph(object):
+    def __init__(self):
+        self.nodes = {}
+    def add_word(self, line):
+        if line in self.nodes:
+            return
+        n = Node(line)
+        for word in flub(line, self.nodes):
+            n.create_edge(self.nodes[word])
+        self.nodes[line] = n
+    def find_shortest_route(self, start, end):
+        if len(start) != len(end):
+            return
+        if start == end:
+            return [start]
+        if not self.nodes[start]:
+            raise Exception("Do not know word %s" % start)
+        if not self.nodes[end]:
+            raise Exception("Do not know word %s" % end)
+        seen = set([self.nodes[start]])
+        heap = [(hamming_distance(start, end), self.nodes[start])]
+        path_hop = {}
+        while heap:
+            node = heapq.heappop(heap)[1]
+            for n2 in node.edges:
+                if n2 in seen:
+                    continue
+                seen.add(n2)
+                dist = hamming_distance(n2.word, end)
+                if dist == 0:
+                    path = [n2.word, node.word]
+                    while path[-1] != start:
+                        path.append(path_hop[path[-1]])
+                    path.reverse()
+                    return path
+                heapq.heappush(heap, (dist, n2))
+                path_hop[n2.word] = node.word
+        return
+
+class Node(object):
+    def __init__(self, word):
+        self.word = word
+        self.edges = set()
+
+    def create_edge(self, node):
+        self.edges.add(node)
+        node.edges.add(self)
+
+def create_cache():
+    f = file('/usr/share/dict/words', 'rb')
+    chars = set(string.lowercase)
+    graph = Graph()
+    for line in f:
+        line = line.strip().lower()
+        if set(line).difference(chars): # not a word as far as we are concerned
+            continue
+        graph.add_word(line)
+    import sys
+    sys.setrecursionlimit(100000)
+    cPickle.Pickler(file('graph.pickle', 'wb'), protocol=2).dump(graph)
+    return graph
+
+def main():
+    try:
+        print "Loading pickle"
+        graph = cPickle.load(file('graph.pickle', 'rb'))
+        print "Finished loading pickle"
+    except IOError:
+        print "Creating cache"
+        graph = create_cache()
+        print "Finished creating cache"
+    print graph.find_shortest_route(sys.argv[1], sys.argv[2])
 
 if __name__ == '__main__':
-    assert len(sys.argv[1]) == len(sys.argv[2])
-    graph = __import__('graph_%d' % len(sys.argv[1])).graph
-    find_transformations(sys.argv[1], sys.argv[2], graph)
+    main()
 
-- 
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