{"id":1807,"date":"2018-02-20T08:24:05","date_gmt":"2018-02-20T16:24:05","guid":{"rendered":"http:\/\/zxi.mytechroad.com\/blog\/?p=1807"},"modified":"2018-08-31T12:27:30","modified_gmt":"2018-08-31T19:27:30","slug":"leetcode-784-letter-case-permutation","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/searching\/leetcode-784-letter-case-permutation\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 784. Letter Case Permutation"},"content":{"rendered":"<p><iframe loading=\"lazy\" title=\"\u82b1\u82b1\u9171 LeetCode 784. Letter Case Permutation - \u5237\u9898\u627e\u5de5\u4f5c EP169\" width=\"500\" height=\"375\" src=\"https:\/\/www.youtube.com\/embed\/LJifc-ehvBM?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n<p>\u9898\u76ee\u5927\u610f\uff1a\u7ed9\u4f60\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c\u6bcf\u4e2a\u5b57\u6bcd\u53ef\u4ee5\u53d8\u6210\u5927\u5199\u4e5f\u53ef\u4ee5\u53d8\u6210\u5c0f\u5199\u3002\u8ba9\u4f60\u8f93\u51fa\u6240\u6709\u53ef\u80fd\u5b57\u7b26\u4e32\u3002<\/p>\n<p>Given a string S, we can transform every letter individually\u00a0to be lowercase or uppercase to create another string.\u00a0 Return a list of all possible strings we could create.<\/p>\n<pre class=\"decode-attributes:false lang:default decode:true\">Examples:\r\nInput: S = \"a1b2\"\r\nOutput: [\"a1b2\", \"a1B2\", \"A1b2\", \"A1B2\"]\r\n\r\nInput: S = \"3z4\"\r\nOutput: [\"3z4\", \"3Z4\"]\r\n\r\nInput: S = \"12345\"\r\nOutput: [\"12345\"]<\/pre>\n<p><strong>Note:<\/strong><\/p>\n<ul>\n<li><code>S<\/code>\u00a0will be a string with length at most\u00a0<code>12<\/code>.<\/li>\n<li><code>S<\/code>\u00a0will consist only of letters or digits.<\/li>\n<\/ul>\n<p><ins class=\"adsbygoogle\" style=\"display: block; text-align: center;\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\" data-ad-client=\"ca-pub-2404451723245401\" data-ad-slot=\"7983117522\">\u00a0<\/ins><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1829\" src=\"http:\/\/zxi.mytechroad.com\/blog\/wp-content\/uploads\/2018\/02\/784-ep169.png\" alt=\"\" width=\"960\" height=\"540\" srcset=\"https:\/\/zxi.mytechroad.com\/blog\/wp-content\/uploads\/2018\/02\/784-ep169.png 960w, https:\/\/zxi.mytechroad.com\/blog\/wp-content\/uploads\/2018\/02\/784-ep169-300x169.png 300w, https:\/\/zxi.mytechroad.com\/blog\/wp-content\/uploads\/2018\/02\/784-ep169-768x432.png 768w\" sizes=\"auto, (max-width: 960px) 100vw, 960px\" \/><\/p>\n<h1><strong>Solution 1: DFS<\/strong><\/h1>\n<p>Time complexity: O(n*2^l), l = # of letters in the string<\/p>\n<p>Space complexity: O(n) + O(n*2^l)<\/p>\n<div class=\"responsive-tabs\">\n<h2 class=\"tabtitle\">C++<\/h2>\n<div class=\"tabcontent\">\n\n<pre class=\"lang:default decode:true \">\/\/ Author: Huahua\r\n\/\/ Running time: 7 ms\r\nclass Solution {\r\npublic:\r\n  vector&lt;string&gt; letterCasePermutation(string S) {\r\n    vector&lt;string&gt; ans;\r\n    dfs(S, 0, ans);\r\n    return ans;\r\n  }\r\nprivate:\r\n  void dfs(string&amp; S, int s, vector&lt;string&gt;&amp; ans) {\r\n    if (s == S.length()) {\r\n      ans.push_back(S);\r\n      return;      \r\n    }\r\n    dfs(S, s + 1, ans);    \r\n    if (!isalpha(S[s])) return;          \r\n    S[s] ^= (1 &lt;&lt; 5);\r\n    dfs(S, s + 1, ans);\r\n    S[s] ^= (1 &lt;&lt; 5);\r\n  }\r\n};<\/pre>\n\n<\/div><h2 class=\"tabtitle\">Java<\/h2>\n<div class=\"tabcontent\">\n\n<pre class=\"lang:java decode:true \">\/\/ Author: Huahua\r\n\/\/ Running time: 8 ms\r\nclass Solution {\r\n  public List&lt;String&gt; letterCasePermutation(String S) {\r\n    List&lt;String&gt; ans = new ArrayList&lt;&gt;();\r\n    dfs(S.toCharArray(), 0, ans);\r\n    return ans;\r\n  }\r\n  \r\n  private void dfs(char[] S, int i, List&lt;String&gt; ans) {\r\n    if (i == S.length) {\r\n      ans.add(new String(S));\r\n      return;\r\n    }    \r\n    dfs(S, i + 1, ans);    \r\n    if (!Character.isLetter(S[i])) return;\r\n    S[i] ^= 1 &lt;&lt; 5;\r\n    dfs(S, i + 1, ans);\r\n    S[i] ^= 1 &lt;&lt; 5;\r\n  }\r\n}<\/pre>\n\n<\/div><h2 class=\"tabtitle\">Python 3<\/h2>\n<div class=\"tabcontent\">\n\n<pre class=\"lang:python decode:true \">\"\"\"\r\nAuthor: Huahua\r\nRunning time: 92 ms\r\n\"\"\"\r\nclass Solution:\r\n  def letterCasePermutation(self, S):\r\n    ans = []\r\n\r\n    def dfs(S, i, n):\r\n      if i == n:\r\n        ans.append(''.join(S))\r\n        return\r\n      \r\n      dfs(S, i + 1, n)      \r\n      if not S[i].isalpha(): return      \r\n      S[i] = chr(ord(S[i]) ^ (1&lt;&lt;5))\r\n      dfs(S, i + 1, n)\r\n      S[i] = chr(ord(S[i]) ^ (1&lt;&lt;5))\r\n    \r\n    dfs(list(S), 0, len(S))\r\n    return ans<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u9898\u76ee\u5927\u610f\uff1a\u7ed9\u4f60\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c\u6bcf\u4e2a\u5b57\u6bcd\u53ef\u4ee5\u53d8\u6210\u5927\u5199\u4e5f\u53ef\u4ee5\u53d8\u6210\u5c0f\u5199\u3002\u8ba9\u4f60\u8f93\u51fa\u6240\u6709\u53ef\u80fd\u5b57\u7b26\u4e32\u3002 Given a string S, we can transform every letter individually\u00a0to be lowercase or uppercase to create another string.\u00a0 Return a list of all possible&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[44,47],"tags":[33,222,121],"class_list":["post-1807","post","type-post","status-publish","format-standard","hentry","category-searching","category-string","tag-dfs","tag-easy","tag-permutation","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/1807","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/comments?post=1807"}],"version-history":[{"count":12,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/1807\/revisions"}],"predecessor-version":[{"id":3788,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/1807\/revisions\/3788"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=1807"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=1807"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=1807"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}