masayang · March 10, 2013 22:50 · Mar 10, 2013
diff --git a/friends.list b/friends.list
@@ -0,0 +1,4 @@
+W, A, B, C
+X, A, B, C, D, Z
+Y, A, B, E
+Z, A, B, D, E
diff --git a/recommendation.py b/recommendation.py
@@ -0,0 +1,25 @@
+from mrjob.job import MRJob
+
+class Recommendation(MRJob):
+    def mapper(self, key, line):
+        input = line.split(',')
+        user, friends = input[0], input[1:]
+        for i in range(len(friends)):
+            f1 = friends[i].strip()
+            for j in range(i+1, len(friends)):
+                f2 = friends[j].strip()
+                if f1 < f2:
+                    yield(f1, f2), 1
+                else:
+                    yield(f2, f1), 1
+
+    def reducer(self, key, values):
+        f1, f2 = key
+        mutual_friends_count = 0
+        for value in values:
+            mutual_friends_count += value
+
+        yield (f1, f2), mutual_friends_count
+
+if __name__ == '__main__':
+    Recommendation.run()
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