选择排序

• 选择排序对冒泡排序进行了改进，每趟都使当前最大项就位
• 选择排序的时间复杂度比冒泡排序稍优：
  对比次数是O( ),交换次数减少为O(n)

def selectionSort(alist):
    for fillslot in range(len(alist)-1,0,-1):
        positionOfMax = 0
        for location in range(1, fillslot + 1):
            if alist[location] > alist[positionOfMax]:
                positionOfMax = location         
        alist[location],alist[positionOfMax] = alist[positionOfMax], alist[location]