Letter Case Permutation
LWC 72: 784. Letter Case Permutation
传送门：784. Letter Case Permutation
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 at most 12.
- S will consist only of letters or digits.
思路： dfs即可，遇到数字跳过，遇到字母，分为两种情况传给子问题。
Java版本：
public List<String> letterCasePermutation(String S) {
all = new ArrayList<>();
backtrack(S.toCharArray(), 0, "");
return all;
}
List<String> all;
public void backtrack(char[] cs, int pos, String ans) {
if (pos == cs.length) {
all.add(ans);
return;
}
else {
if (Character.isAlphabetic(cs[pos])) {
char l = cs[pos];
backtrack(cs, pos + 1, ans + l);
if (l >= 'a' && l <= 'z') l = (char) (l - 'a' + 'A');
else if (l >= 'A' && l <= 'Z') l = (char) (l - 'A' + 'a');
backtrack(cs, pos + 1, ans + l);
}
else {
backtrack(cs, pos + 1, ans + cs[pos]);
}
}
}Python版本：
class Solution(object):
def letterCasePermutation(self, S):
"""
:type S: str
:rtype: List[str]
"""
ans = []
def dfs(S, pos, str):
if pos == len(S):
ans.append(str)
return
else:
if S[pos].isalpha():
letter = S[pos]
dfs(S, pos + 1, str + letter.upper())
dfs(S, pos + 1, str + letter.lower())
else:
dfs(S, pos + 1, str + S[pos])
dfs(S, 0, '')
return ans本文参与 腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。
原始发表：2018年02月18日，如有侵权请联系 cloudcommunity@tencent.com 删除
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