小魚要學數據結構與算法（基於python)—Day13插入排序和謝爾排序

排序和查找

一、知識概覽

本章主要講解六種排序算法中的插入排序和謝爾排序，知識概覽如下：

1.1 插入排序算法

1.2 謝爾排序

二、代碼實現

2.1插入排序

# 插入排序
def insertionSort(alist):
    # index是待插入項位置
    for index in range(1, len(alist)):
        # 新項
        currentvalue = alist[index]
        pos = index
        while pos > 0 and alist[pos - 1] > currentvalue:
            # 倒着依次和前一項比較
            alist[pos] = alist[pos - 1]
            pos = pos - 1
            # pos指向第一個比插入項小的項後面的位置
        alist[pos] = currentvalue
    return alist

2.2 謝爾排序

# 謝爾排序
def shellSort(alist):
    # 間隔設定
    sublistcount = len(alist) // 2
    while sublistcount > 0:
        # 子列表排序
        for startpos in range(sublistcount):
            # 帶間隔的插入排序
            gapinsertionSort(alist, startpos, sublistcount)
        print("After increment of size", sublistcount, "The list is", alist)
        sublistcount = sublistcount // 2
    return alist


def gapinsertionSort(alist, start, gap):
    for i in range(start + gap, len(alist), gap):
        currentvalue = alist[i]
        pos = i
        while pos >= gap and alist[pos - gap] > currentvalue:
            alist[pos] = alist[pos - gap]
            pos = pos - gap
        alist[pos] = currentvalue


lista = [17, 26, 93, 44, 77, 31, 54, 55, 20]
lista1 = insertionSort(lista)
lista2 = shellSort(lista)
print(lista1)
print(lista2)

2.3 輸出

After increment of size 4 The list is [17, 20, 26, 31, 44, 54, 55, 77, 93]
After increment of size 2 The list is [17, 20, 26, 31, 44, 54, 55, 77, 93]
After increment of size 1 The list is [17, 20, 26, 31, 44, 54, 55, 77, 93]
[17, 20, 26, 31, 44, 54, 55, 77, 93]
[17, 20, 26, 31, 44, 54, 55, 77, 93]