# [Sort] Selection Sort

# ⚙️ 정렬 방식

주어진 데이터 중, 최소값을 찾아 맨 앞의 값과 교체함.
해당 최소값을 제외한 나머지 데이터 중 최소값 찾아 그전 최소값 다음에 붙여 넣음.
끝날때 까지 계속.

출처: https://en.wikipedia.org/wiki/Selection_sort (opens new window)

# 📝 구현

# 랜덤 배열 생성

import random as rd
arr = rd.sample(range(1,101), 100)
print(arr)

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# 랜덤 배열 확인

[11, 65, 53, 57, 29, 97, 80, 78, 17, 98, 6, 83, 72, 73, 2, 46, 95, 12, 26, 55, 58, 84, 59, 70, 14, 44, 25, 85, 3, 76, 43, 69, 66, 81, 89, 35, 33, 48, 91, 68, 22, 39, 77, 32, 36, 18, 74, 86, 30, 4, 23, 42, 88, 56, 45, 75, 38, 21, 87, 24, 99, 8, 13, 52, 34, 9, 15, 37, 63, 20, 90, 79, 27, 62, 94, 51, 96, 50, 71, 16, 61, 100, 93, 67, 60, 92, 41, 64, 54, 49, 82, 1, 40, 47, 5, 28, 7, 31, 10, 19]

# 정렬 알고리즘 코드

def selection_sort(array):
for i in range(len(array) - 1):
  min_idx = i
  for j in range(i+1, len(array)):
    if array[min_idx] > array[j]:
      min_idx = j
  array[min_idx], array[i] = array[i], array[min_idx]

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# 정렬 결과 확인

selection_sort(arr)
print(arr)

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[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]

# 🧮 알고리즘 분석

반복문 2중으로 사용 : $O(n^2)$
실제로는 $\frac{n(n-1)}{2}$

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