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  1. Prepare
  2. Python
  3. Collections
  4. DefaultDict Tutorial
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DefaultDict Tutorial

  • TheDugong
     + 5 comments

    Setting the default value to -1 rather than to a list as you suggested:

    from collections import defaultdict

n, m = map(int, input().split())
d = defaultdict(lambda: -1)

for i in range(1, n+1): 
    word = input()
    d[word] = d[word] + ' ' + str(i) if word in d else str(i)

for _ in range(m):
    print(d[input()])