WordSplitPrinter,
WordSplit Printer Material from Lecture 09 will be helpful here. In lecture, we talked about how we can use recursion exploration to print out all permutations of a given string. For example, we could use recursion on the input “goat” to print out: tgoa tgao toga goat gota gaot gato gtoa gtao ogat ogta oagt oatg otga otag agot agto aogt aotg atgo atog toag tago taog Most of these aren’t actual anagrams, because they’re gibberish. We could check which are actual words (like “toga”), but that wouldn’t be enough. There are also cases like “atgo” where the full string isn’t a word, but we can break it into the separate words “at” and “go”. To find all anagrams, then, we need to find the ways we can take one of these permutations and split it into separate English words. That’s where your method, findWordsplits, comes in: public void findWordSplits(String input, TreeSet allWords) { // TODO: Implement this. } The method takes two parameters: input and allWords. input will be a string like “atgo” or “goat” that you’re trying to split into separate words. You do not need to find permutations of input, since that was part of the demo we did in class. input will be a string whose character ordering is already set. allWords is a set containing the words listed in the “words.txt” file — nearly 10,000 English words. allWords is already populated for you! You’ll need to use it when you’re splitting up the input string, since each chunk needs to be an actual word. . Your task is to implement findWordsSplits to find every way you can split input into valid English words, where every character in input is used exactly once. For example, if input is we would expect these two splits to be printed: “goat”, go at goat Other arrangements, such as “g oat” or “goat”, would not be printed because “g”, “goa”, and “t” are not considered words. The main method uses “isawabus” as input. Once findWordsSplits is correctly implemented, you should see the following output: i saw a bus i saw ab us is aw a bus is aw ab us If the exact ordering is not the same, that’s completely fine. I’ve provided an already implemented method in the starter code called printWordsplit: public void printWordSplit(ArrayList words) { // Already implemented for you. } You should call printWordSplit to print out a single arrangement. For the “i saw a bus” example above, you would call printWordSplit passing in an ArrayList containing [“i”, “saw”, “a”, “bus” ] to print it out. findWordSplits is a recursion exploration problem, just like our permutations demo in lecture. Think about how to apply the recursion exploration formula: 1. How do you represent a path of options you’re exploring? o printWordsplit is a major hint — if you need an ArrayList to print a word split, that would also be a convenient way to represent a path. 2. At each step, what are your options? o Consider an example like “isawabus”. We can actually list out every possible option for the next word: i is isa isaw isawa isawab isawabu isawabus Not all of these are words, so you’ll need to check for yourself which ones are valid options using the allWords set. The TreeSet is just a specific type of Set, so you can use any Set methods on it. 3. What do you do when you’ve finished exploring a path? o Just call printWordsplit! Another hint: in your implementation, you will need to use the String’s substring method to split a string into two parts. • To get a substring that contains the first i characters, use str.substring(0, i) where str is the name of your String variable. To get the rest of that string (i.e. everything other than the first i characters), use str.substring(i). If you’re struggling to translate the above into actual code, I strongly recommend revisiting Lecture 09 and see how we applied the same formula to the permutations problem or the password guessing problem. WordSplitChecker Material from Lecture 10 will be helpful here. If you were able to complete WordSplitPrinter, then congratulations! You’ve already done most of the hard work for this last step. In WordSplitChecker
WordSplitPrinter.java
package edu.csc220.recursion;
import java.io.*;
import java.util.*;
public class WordSplitPrinter {
/**
* Finds and prints out every possible way to split the input String into individual, valid English words (including
* if input is itself a single valid word). You must call printWordSplit below to actually print out the results.
*/
public void findWordSplits(String input, TreeSet allWords) {
// TODO: Implement this.
}
/** Prints out a word split, i.e. one particular arrangement of words. This is implemented for you! */
private void printWordSplit(ArrayList words) {
if (words.isEmpty()) {
System.out.println("(empty word list)");
} else {
System.out.print(words.get(0));
for (int i = 1; i < words.size(); i++) {
System.out.print(" " + words.get(i));
}
System.out.println();
}
}
public static void main(String[] args) {
TreeSet dictionary = readWords();
WordSplitPrinter wordSplitPrinter = new WordSplitPrinter();
// Expected to print out:
// i saw a bus
// i saw ab us
// is aw a bus
// is aw ab us
wordSplitPrinter.findWordSplits("isawabus", dictionary);
}
// Reads the "words.txt" file and returns the words in a TreeSet. This is completely implemented for you!
private static TreeSet readWords() {
TreeSet allWords = new TreeSet<>();
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader("words.txt"));
String line;
while ((line = bufferedReader.readLine()) != null) {
if (line.trim().isEmpty()) {
continue;
}
allWords.add(line.toLowerCase());
}
bufferedReader.close();
} catch (IOException exception) {
throw new RuntimeException(exception);
}
return allWords;
}
}
