(董付国)Python 学习笔记---Python控制结构（3）

例 3-13 给定一个包含若干随机整数的列表A，求满足0<=a<=b<n的A[]的最大值。

#高大上的动态规划算法
def maxDifference2(lst):
    diff = -float('inf')    #正无穷:float('inf')负无穷:float('-inf')

    minCurrent = lst[0]

    for value in lst[1:]:
        if value < minCurrent:
            minCurrent = value
        else:
            t = value - minCurrent
            if t > diff:
                diff = t
                result = (minCurrent,value)
    return result[1] - result[0]

A = [1,2,3,4,5,6,9]
print(maxDifference2(A))
            

例 3-14 模拟蒙蒂霍而悖论游戏。
假设你正参加一个有奖游戏节目，并且有3道门可选：其中一个后面是汽车，另外两个后面是山羊。你选择一个门，比如说1号门，主持人当然知道每个门后面是什么并且打开了另一个门，比如说3号们，后面是一只羊。然后主持人问你“你想改选2号门吗？”那么问题来了，改选的话对你会有利吗？

from random import randrange    #randint是返回一个[],
                                #randrange返回一个[)。
def init():
    #返回一个自典，键为3个门号，值为门后面的物品
    result = {i:'goat' for i in range(3)}
    r = randrange(3)
    result[r] = 'car'
    return result

def startgame():
    #获取本次游戏中每个门的情况
    doors = init()
    #获取玩家选择的门号
    #异常处理结构
    while True:
        try:
            firstDoorNum = int(input('Choose a door to open:'))
            assert 0<=firstDoorNum<=2
            break
        except:
            print('Door number must be between {} and {}'.format(0,2))
    #主持人查看另外两个门后的情况
    for door in doors.keys()-{firstDoorNum}:
        #打开其中一个门后面为山羊的门
        if doors[door] == 'goat':
            print('"goat"behind the door',door)
            #获取第三个门号，让玩家纠结
            thirdDoor = (doors.keys() - {firstDoorNum}).pop()
            change = input('Do you want to switch to {}?(y/n):'.format(thirdDoor))
            #如果选择y，就是第三个门，否则就是第一次选择的门
            finalDoorNum = thirdDoor if change == 'y' else firstDoorNum
            if doors[finalDoorNum] == 'goat':
                return 'I win!'
            else:
                return 'You win.'

while True:
    print('='*30)
    print(startgame())
    r = input('Do you want to try once more?(y/n)')
    if r=='n':
        break

运行结果测试：

==============================
Choose a door to open:3
Door number must be between 0 and 2
Choose a door to open:1
"goat"behind the door 0
Do you want to switch to 0?(y/n):y
I win!
Do you want to try once more?(y/n)n