Question

Java

A bigram is a pair of adjacent words in a sequence. Bigrams overlap so that in the sequence "a b. c d", the bigrams are ("a", "b."), ("b.", "c"), ("c", "d"). You will write a simple parser which builds a bigram model based on input text and will allow checking sentences and generating sequences. To do so, you should take advantage of Java’s collection classes including Maps.

Create a class called Bigram. The class will have a constructor which takes a String. A Bigram object’s job is to analyze this single String given to the constructor. You may want to use the constructor to preprocess the input to support the two methods below. Use a Scanner with its default tokenization on the String (don’t call useDelimeter). As long as hasNext() returns true, each call to next() on the Scanner will retrieve the next word. Note that some words will be capitalized differently or contain punctuation. Treat each of those differently (for example, "Dogs", "dogs", and "dogs." are all different strings).

public boolean check(String sentence) (Sentence checking method): Checking a sentence will consist of looking at each (overlapping) pair of adjacent words. If all adjacent pairs in the sentence were seen in your constructor text, your code will return true, otherwise false.

Example:

Bigram x = new Bigram("Bob likes dogs. Bill likes cats. Jane hates dogs.");

x.check("Bob likes cats.") returns true: "Bob likes" and "likes cats." both appear.

x.check("Jane likes cats.") returns false: "Jane likes" does not appear in the input text.

Answer 1

PROGRAM :

import java.util.*;

//class for Bigram

public class Bigram

{

//map for bigram counts

private Map<String,Map<String,Integer>> bigramCounts;

public Bigram(String s)

{

bigramCounts = new HashMap<String,Map<String,Integer>>();

Scanner sc = new Scanner(s);

String c, p = null;

while(sc.hasNext())

{

c = sc.next();

if(p != null)

{

if(bigramCounts.get(p) == null)

{

bigramCounts.put(p, new TreeMap<String,Integer>());

}

if(bigramCounts.get(p).get(c) == null)

{

bigramCounts.get(p).put(c,1);

}

else

{

int count = bigramCounts.get(p).get(c);

bigramCounts.get(p).put(c,count+1);

}

}

p = c;

}

}

//method for check() function

public boolean check(String s)

{

Scanner sc = new Scanner(s);

boolean possible = true;

String c, p = null;

while(sc.hasNext())

{

c = sc.next();

if(p != null)

{

if(bigramCounts.get(p) == null)

{

possible = false;

break;

}

if(bigramCounts.get(p).get(c) == null)

{

possible = false;

break;

}

}

p = c;

}

return possible;

}

//method for generate() function

public String[] generate(String start, int count)

{

String[] generateString = new String[count];

generateString[0] = start;

int i = 1;

while(i < count)

{

if(bigramCounts.get(generateString[i-1]) == null)

{

break;

}

//assign key set using Set

Set<String> ks = bigramCounts.get(generateString[i-1]).keySet();

//assign order list using List

List<String> orderList = new ArrayList<String>(ks);

Collections.reverse(orderList);

//assign maximum frequency is 0

int mfreq = 0;

//assign minimum word frequency

String mwFreq = null;

for(String str : orderList)

{

if(mfreq == 0)

{

mwFreq = str;

mfreq = bigramCounts.get(generateString[i-1]).get(str);

}

else if (bigramCounts.get(generateString[i-1]).get(str)==mfreq)

{

if(str.compareTo(mwFreq) < 0)

{

mwFreq = str;

}

}

else

{

break;

}

}

generateString[i++] = mwFreq;

}

return generateString;

}

//main function

public static void main(String []args)

{

Bigram x = new Bigram("Bob likes dogs. Bill likes cats. Jane hates dogs.");

//call check() method

System.out.println(x.check("Bob likes cats."));

System.out.println(x.check("Jane likes cats."));

Bigram y = new Bigram("The balloon was red. The balloon got bigger and bigger. The balloon popped.");

System.out.print("[");

//call generate method

for(String str: y.generate("The", 3))

{

System.out.print('"'+ str +'"'+" ");

}

System.out.print("]\n");

System.out.print("[");

for(String str:y.generate("popped.", 1))

{

System.out.print('"'+ str +'"'+" ");

}

System.out.print("]\n");

}

}