对于for循环中range（）的某些值，我的代码不会运行

Question

我创建了一个小游戏，让电脑猜出我选择的数字（在1到100之间）。为了提高效率，我让它的第一次猜测总是50，然后它试图通过猜测他最后一次猜测和他能猜到的“更高”或“更低”数字之间的中点来猜测（我知道，这不是一个很好的解释，但你会看到下面的代码）。你知道吗

不管怎样，我注意到它总是能在最多7次尝试中找到答案，至少在我选择的几个数字的情况下。为了验证这个假设，我写了下面的代码：

def take_guess(lower, higher):
    return lower + (higher - lower)/2

lower = 0
higher = 100
t = 1
l = []

for i in range(1,100):
    while True:
        guess = take_guess(lower, higher)
        if guess == i:
            l.append(t)
            t = 1
            break
        elif guess > i:
            higher = guess
            t += 1
            continue
        elif guess < i:
            lower = guess
            t += 1
            continue

print sorted(l)[-1]

问题是，它只能在范围（1,2）或范围（1,3）下运行。如果射程再大，它就跑不动了。有什么原因吗？你知道吗

Answer 1

你的代码非常正确。您只是忘记了在递增i时重置higher和lower的值。你知道吗

下面是代码的工作版本（用于python2）

def take_guess(lower, higher):
    return lower + (higher - lower)/2

lower = 0
higher = 100
t = 1
l = []

for i in range(1,100):
    ###########################
    # This is the only change!
    lower = 0
    higher = 100
    ###########################

    while True:
        # You can watch exactly what's happening by uncommenting the following line:
        # print("i={}\t lower={}\t higher={}".format(i, lower, higher))
        guess = take_guess(lower, higher)
        if guess == i:
            l.append(t)
            t = 1
            break
        elif guess > i:
            higher = guess
            t += 1
            continue
        elif guess < i:
            lower = guess
            t += 1
            continue

print sorted(l)[-1]