Algorithm
本周选择的算法题是：Decode String。
规则
Given an encoded string, return its decoded string.
The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer.
You may assume that the input string is always valid; No extra white spaces, square brackets are well-formed, etc.
Furthermore, you may assume that the original data does not contain any digits and that digits are only for those repeat numbers, k. For example, there won’t be input like 3a or 2[4].
Example 1:
Input: s = "3[a]2[bc]"
Output: "aaabcbc"
Example 2:
Input: s = "3[a2[c]]"
Output: "accaccacc"
Example 3:
Input: s = "2[abc]3[cd]ef"
Output: "abcabccdcdcdef"
Example 4:
Input: s = "abc3[cd]xyz"
Output: "abccdcdcdxyz"
Constraints:
1 <= s.length <= 30sconsists of lowercase English letters, digits, and square brackets'[]'.sis guaranteed to be a valid input.- All the integers in
sare in the range[1, 300].
Solution
class Solution:
def decodeString(self, s: str) -> str:
ans, stack, num = "", [], 0
for char in s:
if char.isdigit():
num = num * 10 + int(char)
elif char == "[":
stack.append((num, ans))
num, ans = 0, ""
elif char == "]":
last_num, last_chars = stack.pop()
ans = last_chars + last_num * ans
else:
ans += char
return ans
Review
How to better manage business logic in your Flutter apps
通篇在讲 Monorepo 的优势，和 Flutter 没太大关系，不如改名为：如何用 Monorepo 更好地管理业务逻辑。
Advanced Python: 9 Best Practices to Apply When You Define Classes
这篇文章还不错，有作者独特的见解，比如作者在介绍 __str__ 和 __repr__ 之间的区别及使用场景时，并不像大多数文章那样，只是简单一句：__repr__ 是给开发者看的，__str__ 是给用户看的，实际上 __repr__ 的字符串是可以通过 eval 重新构建对象的：
class Student:
def __init__(self, first_name, last_name):
self.first_name = first_name
self.last_name = last_name
def __repr__(self):
return f"Student({self.first_name!r}, {self.last_name!r})"
def __str__(self):
return f"Student: {self.first_name} {self.last_name}"
>>> student = Student("David", "Johnson")
>>> student
Student('David', 'Johnson')
>>> print(student)
Student: David Johnson
全文对得起 Best Practices 的说法。
Tip
通过 jekyll-feed 插件为博客添加了订阅功能，订阅地址。