Monthly Archives: August 2014

Remove Duplicates from Sorted Array

Question

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.
Do not allocate extra space for another array, you must do this in place with constant memory.
For example,
Given input array A = [1,1,2],
Your function should return length = 2, and A is now [1,2].

read more

Text Justification

Question

Given an array of words and a length L, format the text such that each line has exactly L 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 L 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.

For example,

words: ["This", "is", "an", "example", "of", "text", "justification."]
L: 16.

Return the formatted lines as:

[
   "This    is    an",
   "example  of text",
   "justification.  "
]

Note: Each word is guaranteed not to exceed Lin length.

Corner Cases:

A line other than the last line might contain only one word. What should you do in this case?
In this case, that line should be left-justified.

My Solution

  public List<String> fullJustify(String[] words, int L) {
    if (words == null || words.length == 0) {
      return Collections.emptyList();
    }
    List<Line> lines = parseToLines(words, L);
    return fillLines(lines, L);
  }

  private List<String> fillLines(List<Line> lines, int L) {
    List<String> output = new ArrayList<String>();
    for (int i = 0; i < lines.size(); i++) {
      Line line = lines.get(i);
      if (line.wordCount() == 1) {
        StringBuilder sb = new StringBuilder();
        sb.append(line.words.get(0));
        sb.append(getSlot(L - line.totalNonSpaceLetterLength()));
        output.add(sb.toString());
      } else if (i == lines.size() - 1) {
        StringBuilder sb = new StringBuilder();
        sb.append(line.words.get(0));
        for (int j = 1; j < line.wordCount(); j++) {
          sb.append(' ');
          sb.append(line.words.get(j));
        }
        sb.append(getSlot(L - line.minimumLength()));
        output.add(sb.toString());
      } else {
        int space = (L - line.totalNonSpaceLetterLength())
            / (line.wordCount() - 1);
        int remain = (L - line.totalNonSpaceLetterLength())
            % (line.wordCount() - 1);
        StringBuilder sb = new StringBuilder();
        sb.append(line.words.get(0));
        for (int j = 1; j <= remain; j++) {
          sb.append(getSlot(space+1));
          sb.append(line.words.get(j));
        }
        for (int j = remain+1; j < line.wordCount(); j++) {
          sb.append(getSlot(space));
          sb.append(line.words.get(j));
        }
        output.add(sb.toString());
      }
    }
    return output;
  }

  private String getSlot(int i) {
    char[] cs = new char[i];
    Arrays.fill(cs, ' ');
    return new String(cs);
  }

  private List<Line> parseToLines(String[] words, int L) {
    List<Line> lines = new ArrayList<Line>();
    Line currentLine = new Line();
    lines.add(currentLine);
    for (String word : words) {
      if (currentLine.minimumLength() + word.length() < L) {
        currentLine.addWord(word);
      } else {
        currentLine = new Line();
        lines.add(currentLine);
        currentLine.addWord(word);
      }
    }
    return lines;
  }

  class Line {

    private List<String> words;
    private int totalLength;

    Line() {
      words = new ArrayList<String>();
      totalLength = 0;
    }

    void addWord(String word) {
      words.add(word);
      totalLength += word.length();
    }

    int wordCount() {
      return words.size();
    }

    int totalNonSpaceLetterLength() {
      return totalLength;
    }

    int minimumLength() {
      return totalLength + words.size() - 1;
    }
  }

read more

[转] 胡适在北京大学毕业典礼上的讲话(1932年6月27日)

【导读】1932年,时任北大文学院院长的胡适,在6月27日毕业典礼上有一段讲话,初载于1932年7月3日《独立评论》,流传至今。胡适谈到的许多问题至今仍然存在:“即便为了吃饭,学问决不会辜负人的。吃饭而不求学问,三年五年之后,你们都要被后进少年淘汰掉的。”