In C++, there are two types of comments, line comments, and block comments.

• The string "//" denotes a line comment, which represents that it and the rest of the characters to the right of it in the same line should be ignored.
• The string "/*" denotes a block comment, which represents that all characters until the next (non-overlapping) occurrence of "*/" should be ignored. (Here, occurrences happen in reading order: line by line from left to right.) To be clear, the string "/*/" does not yet end the block comment, as the ending would be overlapping the beginning.

The first effective comment takes precedence over others.

• For example, if the string "//" occurs in a block comment, it is ignored.
• Similarly, if the string "/*" occurs in a line or block comment, it is also ignored.

If a certain line of code is empty after removing comments, you must not output that line: each string in the answer list will be non-empty.

There will be no control characters, single quote, or double quote characters.

• For example, source = "string s = "/* Not a comment. */";" will not be a test case.

Also, nothing else such as defines or macros will interfere with the comments.

It is guaranteed that every open block comment will eventually be closed, so "/*" outside of a line or block comment always starts a new comment.

Finally, implicit newline characters can be deleted by block comments. Please see the examples below for details.

After removing the comments from the source code, return the source code in the same format.

Example 1:

Input: source = ["/*Test program */", "int main()", "{ ", "  // variable declaration ", "int a, b, c;", "/* This is a test", "   multiline  ", "   comment for ", "   testing */", "a = b + c;", "}"]
Output: ["int main()","{ ","  ","int a, b, c;","a = b + c;","}"]
Explanation: The line by line code is visualized as below:
/*Test program */
int main()
{ 
  // variable declaration 
int a, b, c;
/* This is a test
   multiline  
   comment for 
   testing */
a = b + c;
}
The string /* denotes a block comment, including line 1 and lines 6-9. The string // denotes line 4 as comments.
The line by line output code is visualized as below:
int main()
{ 
  
int a, b, c;
a = b + c;
}

Example 2:

Input: source = ["a/*comment", "line", "more_comment*/b"]
Output: ["ab"]
Explanation: The original source string is "a/*comment\nline\nmore_comment*/b", where we have bolded the newline characters.  After deletion, the implicit newline characters are deleted, leaving the string "ab", which when delimited by newline characters becomes ["ab"].

Constraints:

• 1 <= source.length <= 100
• 0 <= source[i].length <= 80
• source[i] consists of printable ASCII characters.
• Every open block comment is eventually closed.
• There are no single-quote or double-quote in the input.

Solution: Marking the block

The key of this problem is to mark the start and end of a block comment and handling new lines.

Time complexity: O(n)
Space complexity: O(n) -> O(1)

// Author: Huahua
class Solution {
public:
  vector<string> removeComments(vector<string>& source) {
    vector<string> ans;
    bool block = false;
    string output;
    for (string_view line : source) {      
      for (int i = 0, n = line.size(); i < n; ++i) {
        if (block) {
          if (line.substr(i, 2) == "*/") {
            block = false; // leaving block.
            ++i;
          }
          // skip all characters inside the block.
        } else if (line.substr(i, 2) == "/*") {
          block = true; // entering block.
          ++i;
        } else if (line.substr(i, 2) == "//") {
          break;// skip the remaining part of the line.
        } else {
          output += line[i];
        }
      }
      if (!block and !output.empty())
        ans.push_back(std::move(output)); // output cleared.
    }
    return ans;
  }
};

The post 花花酱 LeetCode 722. Remove Comments appeared first on Huahua's Tech Road.

You should pack your words in a greedy approach; that is, pack as many words as you can in each line. Pad extra spaces ' ' when necessary so that each line has exactly maxWidth characters.

Extra spaces between words should be distributed as evenly as possible. If the number of spaces on a line do not divide evenly between words, the empty slots on the left will be assigned more spaces than the slots on the right.

For the last line of text, it should be left justified and no extra space is inserted between words.

Note:

• A word is defined as a character sequence consisting of non-space characters only.
• Each word’s length is guaranteed to be greater than 0 and not exceed maxWidth.
• The input array words contains at least one word.

Example 1:

Input:
words = ["This", "is", "an", "example", "of", "text", "justification."]
maxWidth = 16
Output:
[
   "This    is    an",
   "example  of text",
   "justification.  "
]

Example 2:

Input:
words = ["What","must","be","acknowledgment","shall","be"]
maxWidth = 16
Output:
[
  "What   must   be",
  "acknowledgment  ",
  "shall be        "
]
Explanation: Note that the last line is "shall be    " instead of "shall     be",
             because the last line must be left-justified instead of fully-justified.
             Note that the second line is also left-justified becase it contains only one word.

Example 3:

Input:
words = ["Science","is","what","we","understand","well","enough","to","explain",
         "to","a","computer.","Art","is","everything","else","we","do"]
maxWidth = 20
Output:
[
  "Science  is  what we",
  "understand      well",
  "enough to explain to",
  "a  computer.  Art is",
  "everything  else  we",
  "do                  "
]

Solution: Simulation

Time complexity: O(sum(len(s))
Space complexity: O(sum(len(s))

// Author: Huahua
class Solution {
public:
  vector<string> fullJustify(vector<string> &words, int L) {
    size_t i = 0, n = words.size();
    vector<string> ans;
    
    while (i < n) {
      bool last_line = false;
      int ll = 0;
      vector<string_view> tw;
      
      while (ll <= L && i < n) {
        size_t wl = words[i].length();
        int tll = ll + (tw.size() ? 1 : 0) + wl;
        if (tll > L) break;
        ll = tll;
        tw.push_back(string_view(words[i]));
        if (++i == n) last_line = true;
        if (ll == L) break;
      }

      string line;
      if (!last_line) {
        int tl = 0; 
        for(const auto& w : tw) tl += w.length();
        int avg_space = tw.size()==1 ? 0 : ((L-tl) / (tw.size() - 1));
        int extra_space = tw.size()==1 ? 0 : (L - avg_space * (tw.size() - 1) - tl);        
        for (const auto& w : tw) {
          if (line.length() > 0) {
            line.append(avg_space, ' ');
            if (extra_space > 0) { 
              line += ' '; 
              --extra_space; 
            }
          }
          line += w;
        }
      } else {
        for (const auto& w : tw) {
          if (line.length() > 0) 
            line += ' ';
          line += w;
        }
      }

      line.append(L - line.length(), ' ');
      ans.push_back(std::move(line));
    }
    return ans;
  }
};

The post 花花酱 LeetCode 68. Text Justification appeared first on Huahua's Tech Road.