WayfairOA #1
DFS Subsequences of a String (For MLE)
估计中等评测数据准备中，可先阅读题面
考点（AI 标注）拆分构造
A DFS probl
Example 1
Input:
s = "abc"
Output:
["a", "ab", "abc", "ac", "b", "bc", "c"]
Explanation: The function should return all possible subsequences of the input string "abc" sorted alphabetically, which are: ["a", "ab", "abc", "ac", "b", "bc", "c"].