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 at most12
.S
will consist only of letters or digits.
思路:
深度优先遍历。
void dfs (vector<string>& ret,string S,int i)
{
if(i >= S.length())
{
ret.push_back(S);
return;
} if(isalpha(S[i]))
{
S[i] = tolower(S[i]);
dfs(ret,S,i+); S[i] = toupper(S[i]);
dfs(ret,S,i+);
}
else dfs(ret,S,i+); }
vector<string> letterCasePermutation(string S)
{
vector<string> ret;
dfs(ret,S,);
return ret;
}
参考:
https://leetcode.com/problems/letter-case-permutation/discuss/117180/clean-C++-solution.