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.
Example 1
Input: s = "a1b2"
Output: ["a1b2","a1B2","A1b2","A1B2"]
Example 2
Input: s = "3z4"
Output: ["3z4","3Z4"]
Constraints
- 1 <= s.length <= 12
- s consists of lowercase English letters, uppercase English letters, and digits.
Solution
异或运算可以看作半加运算（不进位的加法）
class Solution {
public:
void dfs(string &s, int pos, vector<string> &res) {
while (pos < s.size() && isdigit(s[pos])) {
pos++;
}
if (pos == s.size()) {
res.emplace_back(s);
return;
}
s[pos] ^= 32;
dfs(s, pos + 1, res);
s[pos] ^= 32;
dfs(s, pos + 1, res);
}
vector<string> letterCasePermutation(string s) {
vector<string> ans;
dfs(s, 0, ans);
return ans;
}
};
