[Python] 순열과 조합

[Python] 순열과 조합

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하나의 리스트에서 모든 조합을 계산하는 방법

1. 순열

itertools.permutations(iterable[, r])

https://www.hackerrank.com/challenges/itertools-permutations/problem

• iterable: iterable한 값
• r: 몇개 씩 묶을 것인지, (미 입력 -> iterable 전체 길이)

  >>> from itertools import permutations
  >>> print list(permutations(['1','2','3']))
  [('1', '2', '3'), ('1', '3', '2'), ('2', '1', '3'), ('2', '3', '1'), ('3', '1', '2'), ('3', '2', '1')]
  >>> 
  >>> print list(permutations(['1','2','3'],2))
  [('1', '2'), ('1', '3'), ('2', '1'), ('2', '3'), ('3', '1'), ('3', '2')]

 

2. 조합

itertools.combinations(iterable, r)

https://www.hackerrank.com/challenges/itertools-combinations/problem?h_r=next-challenge&h_v=zen

• iterable: iterable한 값
• r: 몇개 씩 묶을 것인지

  >>> from itertools import combinations
  >>> print list(combinations('12345',2))
  [('1', '2'), ('1', '3'), ('1', '4'), ('1', '5'), ('2', '3'), ('2', '4'), ('2', '5'), ('3', '4'), ('3', '5'), ('4', '5')]
  >>> 
  >>> A = [1,1,3,3,3]
  >>> print list(combinations(A,4))
  [(1, 1, 3, 3), (1, 1, 3, 3), (1, 1, 3, 3), (1, 3, 3, 3), (1, 3, 3, 3)]