Hackerrank / Iterables and Iterators

링크 :  https://www.hackerrank.com/contests/pythonist3/challenges/iterables-and-iterators/problem

 

Constraints

All the letters in the list are lowercase English letters.

Sample Input

4 
a a c d
2

Sample Output

0.8333

Explanation

All possible unordered tuples of length  comprising of indices from  to  are:

Out of these  combinations,  of them contain either index  or index  which are the indices that contain the letter 'a'.

Hence, the answer is (5/6 = 0.8333).

 

 

Solutions

from itertools import combinations


def solve(n, char, k):
    char = sorted(char)
    cnt = char.count('a')

    data = [i for i in range(len(char))]
    results = list(combinations(data, k))

    total = 0
    for result in results:
        if result[0] < cnt:
            total += 1

    exe = total / len(results)

    return round(exe, 3)


if __name__ == '__main__':
    n = int(input())
    char = list(map(str, input().split(' ')))
    k = int(input())

    print(solve(n, char, k))

 

'a'의 개수를 count한 cnt값을 저장하고

조합 결과는 (1,2),(2,3) 이런식으로 작은 수가 첫번째로 존재한다.

따라서 첫번째 값이 cnt보다 작으면 무조건 'a'를 포함한 조합의 경우이다.

 

 

조합의 경우의 수를 list로 저장하기

from itertools import combinations

list(combinations(data, k))