Text Justification Leet Code Solution | Easy Approach

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Given an array of strings words and a width maxWidth, format the text such that each line has exactly maxWidth characters and is fully (left and right) justified.

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 does 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                  "
]

Constraints:

  • 1 <= words.length <= 300
  • 1 <= words[i].length <= 20
  • words[i] consists of only English letters and symbols.
  • 1 <= maxWidth <= 100
  • words[i].length <= maxWidth

 Text Justification Solutions

Time: O(Σ∣words[i]∣)
Space: O(1)

C++

 class Solution {
 public:
  vector<string> fullJustify(vector<string>& words, size_t maxWidth) {
    vector<string> ans;
    vector<string> row;
    size_t rowLetters = 0;

    for (const string& word : words) {
      // if we put the word in this row, it'll exceed the maxWidth,
      // so we cannot put the word to this row and have to pad spaces to
      // each word in this row
      if (rowLetters + row.size() + word.length() > maxWidth) {
        const int spaces = maxWidth - rowLetters;
        if (row.size() == 1) {
          // pad all spaces after row[0]
          for (int i = 0; i < spaces; ++i)
            row[0] += " ";
        } else {
          // evenly pad spaces to each word (expect the last one) in this row
          for (int i = 0; i < spaces; ++i)
            row[i % (row.size() - 1)] += " ";
        }
        ans.push_back(join(row, ""));
        row.clear();
        rowLetters = 0;
      }
      row.push_back(word);
      rowLetters += word.length();
    }
    ans.push_back(ljust(join(row, " "), maxWidth));

    return ans;
  }

 private:
  string join(const vector<string>& v, const string& c) {
    string s;
    for (auto p = begin(v); p != end(v); ++p) {
      s += *p;
      if (p != end(v) - 1)
        s += c;
    }
    return s;
  }

  string ljust(string s, int width) {
    for (int i = 0; i < s.length() - width; ++i)
      s += " ";
    return s;
  }
};
v

Java

 
 class Solution {
 public:
  vector<string> fullJustify(vector<string>& words, size_t maxWidth) {
    vector<string> ans;
    vector<string> row;
    size_t rowLetters = 0;

    for (const string& word : words) {
      // if we put the word in this row, it'll exceed the maxWidth,
      // so we cannot put the word to this row and have to pad spaces to
      // each word in this row
      if (rowLetters + row.size() + word.length() > maxWidth) {
        const int spaces = maxWidth - rowLetters;
        if (row.size() == 1) {
          // pad all spaces after row[0]
          for (int i = 0; i < spaces; ++i)
            row[0] += " ";
        } else {
          // evenly pad spaces to each word (expect the last one) in this row
          for (int i = 0; i < spaces; ++i)
            row[i % (row.size() - 1)] += " ";
        }
        ans.push_back(join(row, ""));
        row.clear();
        rowLetters = 0;
      }
      row.push_back(word);
      rowLetters += word.length();
    }
    ans.push_back(ljust(join(row, " "), maxWidth));

    return ans;
  }

 private:
  string join(const vector<string>& v, const string& c) {
    string s;
    for (auto p = begin(v); p != end(v); ++p) {
      s += *p;
      if (p != end(v) - 1)
        s += c;
    }
    return s;
  }

  string ljust(string s, int width) {
    for (int i = 0; i < s.length() - width; ++i)
      s += " ";
    return s;
  }
};

Python

  class Solution:
  def fullJustify(self, words: List[str], maxWidth: int) -> List[str]:
    ans = []
    row = []
    rowLetters = 0

    for word in words:
      if rowLetters + len(word) + len(row) > maxWidth:
        for i in range(maxWidth - rowLetters):
          row[i % (len(row) - 1 or 1)] += ' '
        ans.append(''.join(row))
        row = []
        rowLetters = 0
      row.append(word)
      rowLetters += len(word)

    return ans + [' '.join(row).ljust(maxWidth)]

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