有一道面試題： 一個字串"Yes"， 用程式碼實現，輸出其全部大小寫組合，

比如說字串"no"則輸出['no', 'No', 'nO', 'NO']

想到了如下的幾種解法:

方法一：藉助於itertools.combinations

# coding = utf -8

def handle_string(src=""):
    from itertools import combinations
    res = ""
    for char in src:
        res += char.upper() + char.lower()
    words = list(combinations(list(res), 3))
    for i in range(len(src)):
        words = ["".join(item) for item in filter(lambda x:x[i].lower() == src[i].lower(), words)]
    return words

if __name__ == "__main__":
    print(handle_string("Yes"))
 

方法二:藉助於random模組

# coding = utf -8

def handle_string(src=""):
    import random
    sl = src.lower()
    su = src.upper()
    sa = ["".join(list(x+y)) for (i, x) in enumerate(sl) for (j, y) in enumerate(su) if i == j]
    temp = []
    lens = 2 ** len(src)
    while True:
        item = "".join(random.choice(i) for i in sa)
        if item not in temp:
            temp.append(item)
        if len(temp) == lens:
            break
    return temp

if __name__ == "__main__":
    print(handle_string("Yes"))