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  1. # Python 2.5 version
  2. from collections import defaultdict 
  3.  
  4. def list_difference25(a, b):
  5.      """Find (a - b) preserving duplicates and order."""
  6.      # count items in a
  7.      count = defaultdict(int) # item -> number of occurrences  (no OrderedDict to avoid Python 2.7 dependency)
  8.      for x in a:
  9.          count[x] += 1
  10.  
  11.      # remove  items that are in b
  12.      for x in b: 
  13.           count[x] -= 1
  14.      diff = []
  15.      for x in a:
  16.           if count[x] > 0:
  17.              count[x] -= 1
  18.              diff.append(x)
  19.      return diff
  20.  
  21. # Python 2.7 version
  22. from collections import Counter
  23.  
  24. def list_difference(a,  b):
  25.     count = Counter(a)
  26.     count.subtract(b)
  27.     diff = []
  28.     for x in a:
  29.           if count[x] > 0:
  30.              count[x] -= 1
  31.              diff.append(x)
  32.     return diff
  33.  
  34. a, b = raw_input().split(), raw_input().split()
  35. print list_difference25(a, b)
  36. print list_difference(a, b)
Success #stdin #stdout 0.09s 8888KB
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stdin
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a b c b c 
a b c b
stdout
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['c']
['c']
https://ideone.com/ObaSqC
language:
Python (cpython 2.7.16)
created:
12 years ago
visibility:
secret

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