Problem:
Given a string S, we can transform every letter individually to be lowercase or uppercase to create another string. Return a list of all possible strings we could create.
Examples:
Input: S = "a1b2"
Output: ["a1b2", "a1B2", "A1b2", "A1B2"]
Input: S = "3z4"
Output: ["3z4", "3Z4"]
Input: S = "12345"
Output: ["12345"]
Note:
- S will be a string with length between 1 and 12.
- S will consist only of letters or digits.
思路：
Solution (C++):
vector<string> letterCasePermutation(string S) {
vector<string> res;
backtrack(S, 0, res);
return res;
}
void backtrack(string& s, int i, vector<string>& res) {
if (i == s.size()) {
res.push_back(s);
return;
}
backtrack(s, i+1, res);
if (isalpha(s[i])) {
s[i] ^= (1 << 5);
backtrack(s, i+1, res);
}
}
性能：
Runtime: 24 ms Memory Usage: 9.6 MB
思路：
Solution (C++):
性能：
Runtime: ms Memory Usage: MB
