各种排序算法-用Python实现

冒泡排序


# 冒泡排序
def bubble_sort(l):
    length = len(l)
    # 外层循环 length遍,内层循环少一遍
    while length:
        for j in range(length - 1):
            # 找出最大值,然后交换位置到最后
            if l[j] > l[length - 1]:
                l[j], l[length - 1] = l[length - 1], l[j]
        length -= 1


if __name__ == "__main__":
    l = [5, 1, 9, 3, 2, 7]
    bubble_sort(l)
    print l

插入排序

"""
插入排序和冒泡排序的区别在于:
插入排序的前提是:左边是有序的数列
而冒泡排序:相邻的值进行交换,一共进行n次交换
"""


def insert_sort(l):
    # 循环  除第一个数字组成的有序数组 以外的数字
    for i in range(1, len(l)):
        # 每一个数字,依次和有序数组进行比较
        print l[:i]
        for j in range(len(l[:i])):
            if l[i] < l[j]:
                l[i], l[j] = l[j], l[i]


if __name__ == "__main__":
    l = [5, 1, 9, 3, 2, 7]
    print l
    insert_sort(l)
    print("result: " + str(l))

归并排序

def MergeSort(lists):
    if len(lists) <= 1:
        return lists
    num = int(len(lists) / 2)
    # 从中间,进行数据的拆分, 递归的返回数据进行迭代排序
    left = MergeSort(lists[:num])
    right = MergeSort(lists[num:])
    print left
    print "*" * 20
    print right
    print "_" * 20
    return Merge(left, right)


def Merge(left, right):
    r, l = 0, 0
    result = []
    while l < len(left) and r < len(right):
        if left[l] < right[r]:
            result.append(left[l])
            l += 1
        else:
            result.append(right[r])
            r += 1
    result += right[r:]
    result += left[l:]
    print 'result:', result
    return result


if __name__ == "__main__":
    print MergeSort([1, 2, 3, 4, 5, 6, 7, 90, 21, 23, 45])

快速排序

def quick_sort(l, start, end):
    i = start
    j = end
    # 结束排序
    if i >= j:
        return
    # 保存首个数值
    key = l[i]
    # 一次排序,i和j的值不断的靠拢,然后最终停止,结束一次排序
    while i < j:
        # 和最右边的比较,如果>=key,然后j-1,慢慢的和前一个值比较;如果值<key,那么就交换位置
        while i < j and key <= l[j]:
            print key, l[j], '*' * 30
            j -= 1
        l[i] = l[j]
        # 交换位置后,然后在和最左边的值开始比较,如果<=key,然后i+1,慢慢的和后一个值比较;如果值>key,那么就交换位置
        while i < j and key >= l[i]:
            print key, l[i], '*' * 30
            i += 1
        l[j] = l[i]
    l[i] = key
    # 左边排序
    quick_sort(l, start, j-1)
    # 右边排序
    quick_sort(l, i+1, end)


if __name__ == "__main__":
    l = [5, 1, 9, 3, 2, 7]
    quick_sort(l, 0, len(l) - 1)
    print l

选择排序

"""
选择排序和冒泡排序的区别在于:
选择排序的前提是:找到最大值的位置,最后才进行1次交换
而冒泡排序:相邻的值进行交换,一共进行n次交换
"""


def selection_sort(l):
    length = len(l) - 1

    while length:
        index = length
        # 第一个数字,和后面每一个数字进行对比,找出最大值,放到最后!!
        for j in range(length):
            if l[j] > l[index]:
                index = j
        l[length], l[index] = l[index], l[length]
        print len(l) - length, l
        length -= 1


if __name__ == "__main__":
    l = [5, 1, 9, 3, 2, 7]
    print l
    selection_sort(l)
    print("result: " + str(l))

希尔排序

def insert_sort(l, start, increment):
    for i in range(start+increment, len(l), increment):
        for j in range(start, len(l[:i]), increment):
            if l[i] < l[j]:
                l[i], l[j] = l[j], l[i]
    print increment, '--',l
    return l

def shell_sort(l, increment):
    # 依次进行分层
    while increment:
        # 每一层,都进行n次插入排序
        for i in range(0, increment):
            insert_sort(l, i, increment)
        increment -= 1
    return l

if __name__ == "__main__":
    l = [5, 2, 9, 8, 1, 10, 3, 4, 7]
    increment = len(l)/3+1 if len(l)%3 else len(l)/3
    print "开始", l
    l = shell_sort(l, increment)
    print "结束", l

树递归

class Node():
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right

def midRecusion(node):
    if node is None:
        return
    midRecusion(node.left)
    print node.value,
    midRecusion(node.right)

def midIterator(node):
    stack = []
    while stack or node:
        if node is not None:
            stack.append(node)
            node = node.left
        else:
            node = stack.pop(-1)
            print node.value,
            node = node.right

if __name__ == "__main__":
    node = Node("D", Node("B", Node("A"), Node("C")), Node("E", right=Node("G", left=Node("F"))))

    print('\n中序遍历<递归>:')
    midRecusion(node)

    print('\n中序遍历<迭代>:')
    midIterator(node)

更新冒泡排序

'''
迭代使用的是循环结构。
递归使用的是选择结构。
'''

# 递归求解
def calculate(l):
    if len(l) <= 1:
        return l[0]
    value = calculate(l[1:])
    return 10**(len(l) - 1) * l[0] + value


# 迭代求解
def calculate2(l):
    result = 0
    while len(l) >= 1:
        result += 10 ** (len(l)-1) * l[0]
        l = l[1:]
    return result


l1 = [1, 2, 3]
l2 = [4, 5]
sum = 0
result = calculate(l1) + calculate(l2)
# result = calculate2(l1) + calculate2(l2)
print(result)

posted on 2018-09-23 17:26  星辰之衍  阅读(99)  评论(0编辑  收藏

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