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  1. Prepare
  2. Mathematics
  3. Combinatorics
  4. Sherlock and Pairs
  5. Discussions

Sherlock and Pairs

  • dingma129
     + 0 comments

    a python3 solution

    from collections import Counter
def solve(a):
    C = Counter(a)
    return sum(n*(n-1) for n in C.values())