Python四大排序算法

冒泡排序,选择排序,插入排序,快速排序

冒泡排序

alist = list(range(10))
random.shuffle(alist)
print("排序前:",alist)

def bubble(alist):
    """冒泡排序"""
    for j in range(0,len(alist)-1):
        count = 0
        for i in range(0,len(alist)-1-j):
            if alist[i]>alist[i+1]:
                alist[i],alist[i+1] = alist[i+1],alist[i]
                count += 1
        if 0 == count :
            break
    return alist

alist = bubble(alist)
print("排序后:",alist)

选择排序

alist = list(range(10))
random.shuffle(alist)
print("排序前:",alist)

def selectionSort(alist):
    """选择排序"""
    for i in range(len(alist)-1):
        for j in range(i+1,len(alist)):
            if alist[i] > alist[j]:
                alist[i] , alist[j] = alist[j] , alist[i]
                
    return alist
alist = selectionSort(alist)
print("排序后:",alist)

插入排序

alist = list(range(10))
random.shuffle(alist)
print("排序前:",alist)

def insertSort(alist):
    """插入排序"""
    for i in range(1,len(alist)):
        for j in range(i,0,-1):
            if alist[j-1] > alist[j]:
                alist[j] , alist[j-1] = alist[j-1] , alist[j]
            else:
                break
                
    return alist
alist = insertSort(alist)
print("排序后:",alist)

快速排序

alist = list(range(10))
random.shuffle(alist)
print("排序前:",alist)

def fastSort(alist,first,last):
    """快速排序"""
    """
    :first 左边开始点
    :last 右边结束点
    """
    
    if last <= first:
        return  
    mid_value = alist[first]
    left = first
    right = last
    while left < right:
        while left < right and alist[right] >= mid_value:
            right -= 1
        alist[left] = alist[right]

        while left < right and alist[left] < mid_value:
            left += 1
        alist[right] = alist[left]
        
    # left == right
    alist[left] = mid_value
    
    fastSort(alist,first,left-1)
    fastSort(alist,left+1,last)
    
#     return alist
                
fastSort(alist,0,len(alist)-1)
print("排序后:",alist)