{"id":8715,"date":"2021-11-15T11:27:28","date_gmt":"2021-11-15T19:27:28","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=8715"},"modified":"2021-11-15T11:28:03","modified_gmt":"2021-11-15T19:28:03","slug":"leetcode-2075-decode-the-slanted-ciphertext","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/simulation\/leetcode-2075-decode-the-slanted-ciphertext\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 2075. Decode the Slanted Ciphertext"},"content":{"rendered":"\n

A string originalText<\/code> is encoded using a slanted transposition cipher<\/strong> to a string encodedText<\/code> with the help of a matrix having a fixed number of rows<\/strong> rows<\/code>.<\/p>\n\n\n\n

originalText<\/code> is placed first in a top-left to bottom-right manner.<\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n

The blue cells are filled first, followed by the red cells, then the yellow cells, and so on, until we reach the end of originalText<\/code>. The arrow indicates the order in which the cells are filled. All empty cells are filled with ' '<\/code>. The number of columns is chosen such that the rightmost column will not be empty<\/strong> after filling in originalText<\/code>.<\/p>\n\n\n\n

encodedText<\/code> is then formed by appending all characters of the matrix in a row-wise fashion.<\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n

The characters in the blue cells are appended first to encodedText<\/code>, then the red cells, and so on, and finally the yellow cells. The arrow indicates the order in which the cells are accessed.<\/p>\n\n\n\n

For example, if originalText = \"cipher\"<\/code> and rows = 3<\/code>, then we encode it in the following manner:<\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n

The blue arrows depict how originalText<\/code> is placed in the matrix, and the red arrows denote the order in which encodedText<\/code> is formed. In the above example, encodedText = \"ch ie pr\"<\/code>.<\/p>\n\n\n\n

Given the encoded string encodedText<\/code> and number of rows rows<\/code>, return the original string<\/em> originalText<\/code>.<\/p>\n\n\n\n

Note:<\/strong> originalText<\/code> does not<\/strong> have any trailing spaces ' '<\/code>. The test cases are generated such that there is only one possible originalText<\/code>.<\/p>\n\n\n\n

Example 1:<\/strong><\/p>\n\n\n\n

Input:<\/strong> encodedText = \"ch   ie   pr\", rows = 3\nOutput:<\/strong> \"cipher\"\nExplanation:<\/strong> This is the same example described in the problem description.\n<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> encodedText = \"iveo    eed   l te   olc\", rows = 4\nOutput:<\/strong> \"i love leetcode\"\nExplanation:<\/strong> The figure above denotes the matrix that was used to encode originalText. \nThe blue arrows show how we can find originalText from encodedText.\n<\/pre>\n\n\n\n
Example 3:<\/strong><\/p>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> encodedText = \"coding\", rows = 1\nOutput:<\/strong> \"coding\"\nExplanation:<\/strong> Since there is only 1 row, both originalText and encodedText are the same.\n<\/pre>\n\n\n\n
Example 4:<\/strong><\/p>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> encodedText = \" b  ac\", rows = 2\nOutput:<\/strong> \" abc\"\nExplanation:<\/strong> originalText cannot have trailing spaces, but it may be preceded by one or more spaces.\n<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n
  • 0 <= encodedText.length <= 106<\/sup><\/code><\/li>
  • encodedText<\/code> consists of lowercase English letters and ' '<\/code> only.<\/li>
  • encodedText<\/code> is a valid encoding of some originalText<\/code> that does not<\/strong> have trailing spaces.<\/li>
  • 1 <= rows <= 1000<\/code><\/li>
  • The testcases are generated such that there is only one<\/strong> possible originalText<\/code>.<\/li><\/ul>\n\n\n\n
    Solution: Simulation<\/strong><\/h2>\n\n\n\n
    Time complexity: O(n)
    Space complexity: O(n)<\/p>\n\n\n\n
    \n
    C++<\/h2>\n
    \n\n
    \n\/\/ Author: Huahua\nclass Solution {\npublic:\n  string decodeCiphertext(string encodedText, int rows) {\n    const int cols = encodedText.size() \/ rows;    \n    string ans;\n    ans.reserve(encodedText.size());\n    for (int i = 0; i < cols; ++i)\n      for (int j = 0; j < rows && i + j < cols; ++j)      \n        ans += encodedText[j * cols + j + i];\n    while (ans.size() && !isalpha(ans.back())) ans.pop_back();\n    return ans;\n  }\n};\n<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
    A string originalText is encoded using a slanted transposition cipher to a string encodedText with the help of a matrix having a fixed number of rows rows. originalText is placed first in a top-left…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[48],"tags":[177,179,4],"class_list":["post-8715","post","type-post","status-publish","format-standard","hentry","category-simulation","tag-medium","tag-simulation","tag-string","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/8715","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=8715"}],"version-history":[{"count":2,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/8715\/revisions"}],"predecessor-version":[{"id":8717,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/8715\/revisions\/8717"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=8715"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=8715"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=8715"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}