.
题目
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.
.
代码
class Solution {
public:
void backtrack(string S, int idx, set<string>& res) {
if(idx == S.length())
{
res.insert(S);
return;
}
for(int i = idx; i<S.length(); i++)
{
if(S[i] >= '0' && S[i] <= '9')
continue;
else
{
S[i] ^= (1<<5);
res.insert(S);
backtrack(S, i+1, res);
S[i] ^= (1<<5);
}
}
return;
}
vector<string> letterCasePermutation(string S) {
vector<string> res;
set<string> res_set;
if(S.length() < 1)
return res;
res_set.insert(S);
for(int i = 0; i<S.length(); i++)
{
if(S[i] <= '9' && S[i] >= '0')
continue;
backtrack(S, i, res_set);
}
for(set<string>::iterator iter = res_set.begin(); iter!=res_set.end(); iter++)
res.push_back(*iter);
return res;
}
};