Problem 7: Double Ones (100pts)

Problem

Write a function that takes in a number and determines if the digits contain two adjacent 1s. (Reviewing this problem in Lab 01 might be helpful here!)

编写一个函数，接受一个数字作为参数，并判断其数字中是否包含两个相邻的 1。（回顾 Lab 01 中的 这个问题 可能会有所帮助！）

def double_ones(n):
    """Return true if n has two ones in a row.

    >>> double_ones(1)
    False
    >>> double_ones(11)
    True
    >>> double_ones(2112)
    True
    >>> double_ones(110011)
    True
    >>> double_ones(12345)
    False
    >>> double_ones(10101010)
    False
    """
    "*** YOUR CODE HERE ***"

Hints

• 可以使用 str 逃课（）

• 大致思路：取最后两位看看是不是11，如果不是，去掉最后一位再判断

• while 循环和递推都很好写

Solutions

使用 while 循环。当 n 只剩一位时退出循环。

def double_ones(n):
    # Loop while the number n still has at least two digits remaining (n >= 10).
    while n >= 10:
        # Check the last two digits: n % 100 will give the last two digits.
        # If the last two digits are 11, we've found our pattern.
        if n % 100 == 11:
            return True

        # Remove the last digit by performing integer division by 10.
        n = n // 10

    # A single-digit number can never have "11".
    return False

---

递归：

def double_ones(n):
    # If the number is less than 10 (single digit), it cannot have '11'.
    if n < 10:
        return False

    # If the last two digits (n % 100) are 11, the condition is met.
    if n % 100 == 11:
        return True

    # Remove the last digit (n // 10) and recursively call the function.
    return double_ones(n // 10)

---

str 逃课：

def double_ones(n):
    return '11' in str(n)