What is the best approach to solve the "To Lower Case" problem?

The best approach is often to use a built-in method like `toLowerCase()`. However, if not available, manually processing characters one-by-one is a viable alternative.

Does the "To Lower Case" problem require using built-in string methods?

No, but using built-in methods like `toLowerCase()` is the most efficient approach. The problem can also be solved by manually iterating through the string.

How do I optimize the "To Lower Case" solution for large strings?

You should ensure a single pass over the string with an O(n) time complexity. Avoid unnecessary string modifications or copies to save space.

Can I solve the "To Lower Case" problem without converting the string to a new one?

Yes, in languages with mutable strings, you can modify the string in place, but in most languages, strings are immutable, requiring a new one to be created.

Are there any edge cases for the "To Lower Case" problem?

Yes, edge cases include strings with no uppercase letters or empty strings. Both should return the string unchanged or an empty string.

#709

Easy

auto_awesomeString-driven solution strategy

LeetCode 题解工作台

转换成小写字母

给你一个字符串 s ，将该字符串中的大写字母转换成相同的小写字母，返回新的字符串。示例 1：输入： s = "Hello" 输出： "hello" 示例 2：输入： s = "here" 输出： "here" 示例 3：输入： s = "LOVELY" 输出： "lovely" 提示： 1 …

字符串

题目描述

给你一个字符串 s ，将该字符串中的大写字母转换成相同的小写字母，返回新的字符串。

示例 1：

输入：s = "Hello"
输出："hello"

示例 2：

输入：s = "here"
输出："here"

示例 3：

输入：s = "LOVELY"
输出："lovely"

提示：

1 <= s.length <= 100
s 由 ASCII 字符集中的可打印字符组成

lightbulb

解题思路

方法一：模拟

我们可以遍历字符串，对于每个大写字母，将其转换为小写字母。最后返回转换后的字符串即可。

时间复杂度 $O(n)$ ，其中 $n$ 为字符串的长度。忽略答案的空间消耗，空间复杂度 $O(1)$ 。

1

2

3

4

class Solution:
    def toLowerCase(self, s: str) -> str:
        return "".join([chr(ord(c) | 32) if c.isupper() else c for c in s])

speed

复杂度分析

指标	值
时间	Depends on the final approach
空间	Depends on the final approach

psychology

面试官常问的追问

外企场景

question_mark
Candidates should demonstrate a solid understanding of string manipulation and be able to articulate trade-offs in terms of efficiency and readability.
question_mark
The problem tests a candidate's ability to think about edge cases, like handling strings that contain no uppercase characters.
question_mark
The interviewer will look for clarity in how the candidate justifies their choice of approach, particularly regarding the use of built-in methods vs. manual implementations.

warning

常见陷阱

外企场景

error
Candidates may use the built-in function without understanding its internal workings, missing an opportunity to demonstrate algorithmic thinking.
error
Forgetting to handle cases where no uppercase letters exist in the string can lead to unnecessary processing or incorrect assumptions.
error
Failing to optimize for space complexity by repeatedly modifying the string (in languages that don't handle immutability) can lead to inefficient solutions.

swap_horiz

进阶变体

外企场景

arrow_right_alt
Convert a string to uppercase instead of lowercase.
arrow_right_alt
Handle case insensitivity by converting both uppercase and lowercase characters to a common case.
arrow_right_alt
Process a string in place to reduce space complexity, if mutable strings are allowed.

help

常见问题

外企场景

继续练习

#712 两个字符串的最小ASCII删除和 #720 词典中最长的单词 #721 账户合并