Question

In Java,

Write a function to perform bucket sort on a list of strings.Test the function to see if it really works in linear time on average. Finally, compare the performance of the function with Java sort method for lists.

Answer 1

Bucket sort on list of Strings

public void sort(String[] array)

{

if(array.length == 0)

return ;

//find the max length

int max=0;

for(int i=1; i<array.length; i++)

{

//update max length

if(max < array[i].length())

max=array[i].length();

}

//initialize the buckets

int bucketCount=26; //alphabets

//buckets in maps

HashMap<Character, Vector<String>> buckets=new HashMap<Character, Vector<String>>(bucketCount);

//create the buckets

char a='a';

for(int i=0; i<=bucketCount; i++; a++)

{

buckets.put(a, new Vector<String>());

}

//assign String array values into the buckets

for(int i=0; i<array.length; i++)

{

//get the first letter of the String word

String current=array[i];

char letter=current.toLowerCase().charAt(0);

buckets.get(letter).add(array[i]);

}

//sort the buckets and put them into input array

int index=0;

for(char key='a'; key<='z'; key++)

{

//retrieve the bucket

Vector<String> bucket=buckets.get(key);

//perform sort on bucket

for(int i=1; i<bucket.size(); i++)

{

String temp=bucket.get(i);

bucket.remove(i);

int j;

for(j=i-1; j>=0 && bucket.get(j).compareToIgnoreCase(temp) > 0; j--)

{

bucket.add(j+1, bucket.get(j));

bucket.remove(j);

}

bucket.add(j+1, temp);

}

//pile the current bucket back into array

for(int j=0; j<bucket.size(); j++)

array[index++]=bucket.get(j);

  }

}