0068. Text Justification

https://leetcode.com/problems/text-justification

Description

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

ac

class Solution {
    public List<String> fullJustify(String[] words, int maxWidth) {
        // edge cases

        int i = 0, n = words.length;
        List<String> res = new ArrayList<String>();
        StringBuilder sb = new StringBuilder();

        while (i < n) {
            sb.setLength(0); // restart a new line
            // how many words in this line? what is the baseSpace? how many empty slot have extra space?
            int[] info = wordsInLine(words, i, maxWidth);

            if (info[0] == 1) { // only one word
                sb.append(words[i]).append(generateSpace(maxWidth - words[i].length())); // left justify
                i++;
            } else if (i + info[0] >= words.length) { // last line
                while (info[0]-- > 0) {
                    sb.append(words[i++]);
                    if (sb.length() < maxWidth) sb.append(" ");
                }
                if (sb.length() < maxWidth) sb.append(generateSpace(maxWidth - sb.length())); // pad with space
            } else { // normal situation
                while (info[0]-- > 0) { // append x words
                    sb.append(words[i++]);
                    // append space
                    if (info[0] != 0) { // no need to append in last word
                        int spaceCnt = info[2]-- > 0 ? info[1] + 1 : info[1];
                        sb.append(generateSpace(spaceCnt));
                    }
                }
            }
            // add this line to result
            res.add(sb.toString());
        }

        return res;
    }

    private int[] wordsInLine(String[] words, int start, int maxWidth) {
        int len = 0, wordLen = 0, cnt = 0;
        for (int i = start; i < words.length; i++) {
            len += words[i].length();
            if (len > maxWidth) break;
            cnt++; // add one word
            wordLen += words[i].length();
            len++; // add one space
        }
        // base space of empty slot
        int baseSpace = cnt > 1 ? (maxWidth - wordLen) / (cnt - 1) : 0;
        int extraSpaceCnt = cnt > 1 ? (maxWidth - wordLen) % (cnt - 1) : 0;
        return new int[]{cnt, baseSpace, extraSpaceCnt};
    }

    private String generateSpace(int n) {
        StringBuilder sb = new StringBuilder();
        while (sb.length() < n) {
            sb.append(" ");
        }
        return sb.toString();
    }
}

/*
its just implementation dirty work. for each line: how many words in this line? what is the baseSpace? how many empty slot have extra space?  Then process accordingly: 1) just one word; 2) last line; 3) normal situation
*/