notes/OJ notes/pages/Leetcode Letter-Case-Combination.md
2022-07-20 14:25:33 +08:00

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# Leetcode Letter-Case-Combination
#### 2022-07-20 14:19
> ##### Algorithms:
> #algorithm #backtrack
> ##### Difficulty:
> #coding_problem #difficulty-medium
> ##### Additional tags:
> #leetcode
> ##### Revisions:
> N/A
##### Related topics:
```expander
tag:#backtrack
```
##### Links:
- [Link to problem](https://leetcode.com/problems/letter-case-permutation/)
___
### Problem
Given a string `s`, you can transform every letter individually to be lowercase or uppercase to create another string.
Return _a list of all possible strings we could create_. Return the output in **any order**.
#### Examples
**Example 1:**
```
**Input:** s = "a1b2"
**Output:** ["a1b2","a1B2","A1b2","A1B2"]
```
**Example 2:**
```
**Input:** s = "3z4"
**Output:** ["3z4","3Z4"]
```
#### Constraints
**Constraints:**
- `1 <= s.length <= 12`
- `s` consists of lowercase English letters, uppercase English letters, and digits.
### Thoughts
> [!summary]
> This is a #backtrack problem.
### Solution