菜鸟的每日力扣系列——1576. 替换所有的问号

def modifyString(s: str) -> str:
    word = ["a", "b", "c"]
    mylist = list(s)
    n = len(mylist)
    if n == 1 and mylist[0] == '?':
        mylist[0] = word[0]  # 只有一位且是‘？’的情况
    else:
        for i in range(n):
            if i == 0 and mylist[i] == '?':  # '?'出现在字符串开头的情况
                for c in word:
                    if c != mylist[i+1]:
                        mylist[i] = c
                        break
            elif i == n - 1 and mylist[i] == '?':  # '?' 出现在字符串结尾的情况
                for c in word:
                    if c != mylist[i-1]:
                        mylist[i] = c
                        break
            else:
                if mylist[i] == '?':
                    for c in word:
                        if c != mylist[i-1] and c != mylist[i+1]:
                            mylist[i] = c
    return "".join(mylist)


s = "?zs"
print(modifyString(s))  # azs