Text formatting: Get one line of text

Solving Sub-problem 1: fit as many words as you can on one line (of at most 30 characters)

Question:

What would you do if someone ask you to "fit as many words as possible on a line of N characters in length ???

To get a sense of the problem, use a concrete example:

Here are some words:

word[0] = "WE" word[1] = "hold" word[2] = "these" word[3] = "Truths" word[4] = "to" word[5] = "be" word[6] = "self-evident," word[7] = "that" word[8] = "all"

Here is the line with as many words fitted in:

012345678901234567890123456789 >WE hold these Truths to be (next word is: self-evident, and does not fit)

How would you fit as many words as you can on a line of 30 spaces ?

The common-sense algorithm is as follows:

Add the first word to the line as long as the next word fits on the line { Add the next word to the line; }

Example:

String[] words = new String[10000]; int numWords = 35 word[0] = "WE" word[1] = "hold" word[2] = "these" word[3] = "Truths" word[4] = "to" word[5] = "be" word[6] = "self-evident," word[7] = "that" word[8] = "all" word[9] = "Men" word[10] = "are" word[11] = "created" word[12] = "equal," word[13] = "that" word[14] = "they" .... (and so on)

Add first word: 012345678901234567890123456789 line = We|
Check if next word (hold) fits: 012345678901234567890123456789 line = We| +hold Yes, add next word (hold): 012345678901234567890123456789 line = We hold|
Check if next word (these) fits: 012345678901234567890123456789 line = We hold| +these Yes, add next word (these): 012345678901234567890123456789 line = We hold these|

Refining the algorithm

How do we know which word is the next word that needs to be fitted into the line:

We need more information...

Let's use a variable currWord which contains the index in the array of words

currWord will point to the next word that will be fitted in the line.

Example:

String[] words = new String[10000]; int numWords = 35 int currWord; word[0] = "WE" word[1] = "hold" word[2] = "these" word[3] = "Truths" word[4] = "to" word[5] = "be" word[6] = "self-evident," word[7] = "that" word[8] = "all" word[9] = "Men" word[10] = "are" word[11] = "created" word[12] = "equal," word[13] = "that" word[14] = "they" .... (and so on)

currWord = 0; Add word[currWord] (word[0] = "WE"); currWord++; (point to next word) 012345678901234567890123456789 line = We|
Check if word[currWord] (= word[1]) fits: 012345678901234567890123456789 line = We| +hold Yes, add word[currWord] (= word[1]): currWord++; (point to next word) 012345678901234567890123456789 line = We hold|
Check if word[currWord] (= word[2]) fits: 012345678901234567890123456789 line = We hold| +these Yes, add word[currWord] (= word[1]): currWord++; (point to next word) 012345678901234567890123456789 line = We hold these|

Putting the algorithm as a method

Recall that algorithms in the form of a method is most practical
To cast the algorithm in the form of a method, we need to determine:
Inputs and outputs of the readOneLine() method:

Ideal implementation:

Pass in all necessary information (as parameters)
Have the method perform the task and update parameters

Ideal implementation in method form:

/* ------------------------------------------------------------ The readOneLine() method must update the currWord parameter We must pass the parameter currWord by-reference ! ------------------------------------------------------------ */ public static String readOneLine( int currWord, String[] w, int maxLineLength ) { String line; // Line with as many words as possible line = w[ currWord ]; // Add current word as first word currWord = currWord + 1; // Get next word while ( currWord < numWords && line.length() + 1 + w[currWord].length() <= maxLineLength ) { // Next word fits; add next word to line line = line + " " + w[ currWord ]; // Add next word to line currWord = currWord + 1; // Get next word } return( line ); }

Explanation:

We pass in the parameters currWord, the array of words as String[] w and the maximum line length as maxLineLength
We can return the constructed line using return( line )
HOWEVER, this ideal solution will not work, because:
Solution:

Java Program:

import java.io.*; import java.util.Scanner; public class FormatText2 { public static final int NCHARS_IN_LINE = 30; public static String[] words = new String[10000]; // Hold words in input file public static int currWord; // Current word public static int numWords; // Count # words in input public static int readInput( Scanner in, String[] w ) { int nWords = 0; while ( in.hasNext() ) { w[nWords] = in.next(); // Read next string (word) nWords++; // Count # words AND use next // array element for next word } return( nWords ); } /* ================================================================== readOneLine(w, maxLineLength): get one line of text from w[] (<= maxLineLength characters) Starts getting words from w[currLine] =================================================================== */ public static String readOneLine( String[] w, int maxLineLength ) { String line; line = w[ currWord ++ ]; while ( currWord < numWords && line.length() + 1 + w[currWord].length() <= maxLineLength ) { line = line + " " + w[ currWord++ ]; // Add word to line } return(line); } /* ======================================= main(): test the readOneLine() method ======================================= */ public static void main(String[] args) throws IOException { if ( args.length == 0 ) { System.out.println( "Usage: java FormatText2 inputFile"); System.exit(1); } File myFile = new File( args[0] ); // Open file "inp2" Scanner in = new Scanner(myFile); // Make Scanner obj with opened file String nextLine; // Read input from data file numWords = readInput( in, words ); currWord = 0; while ( currWord < numWords ) { nextLine = readOneLine( words, NCHARS_IN_LINE ); System.out.println(" 012345678901234567890123456789"); System.out.println(" >" + nextLine + "\n"); } } }

Example:

Input file:

WE hold these Truths to be self-evident, that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the Pursuit of Happiness.

Output:

012345678901234567890123456789 >WE hold these Truths to be 012345678901234567890123456789 >self-evident, that all Men are 012345678901234567890123456789 >created equal, that they are 012345678901234567890123456789 >endowed by their Creator with 012345678901234567890123456789 >certain unalienable Rights, 012345678901234567890123456789 >that among these are Life, 012345678901234567890123456789 >Liberty and the Pursuit of 012345678901234567890123456789 >Happiness.

Example Program: (Demo above code)

Prog file: click here
Input file 1 (small): click here
Input file 2 (large): click here

How to run the program:

Right click on link and save in a scratch directory
To compile: javac FormatText2.java
To run: java FormatText2 inp1
Or: java FormatText2 inp2

Programming note

The following variables store related information:

public static String[] words = new String[10000]; // words[] hold words from input public static int currWord; // Current word in words[] public static int numWords; // # words in words[]

So it is a good idea to define these variable in the same area in the Java program
We have determined that:
So we also define the other related variables as class variable...
(BTW, words and numWords could have been defined as local variables).