I am writing a program for an assignment, but when I tried to adapt merge sort to work on a String (to sort alphabetically), it generates a seemingly random order of titles, as seen below. I asked this question some time ago, and got no real answers, and so I felt like I needed to phrase it better and include my full code.
By Title Ascending
Titanic, 1997 by Paramount, Marvel's The Avengers, 2012 by Disney Harry Potter and the Deathly Hallows Part 2, 2012 by Warner Brothers Furious 7, 2015 by Universal Avengers: Age of Ultron, 2015 by Disney Avatar, 2009 by Fox Star Wars: The Force Awakens, 2015 by Disney Jurassic World, 2015 by Universal Avengers: Infinity War, 2018 by Disney Black Panther, 2018 by Disney
I have to arrange alphabetically specifically using merge sort that I write myself, and while I have tried all sorts of different configurations of the compareTo statement, like:
else if ((a[j].getTitle()).compareTo(a[i].getTitle()) > 0)
else if ((a[i].getTitle()).compareTo(a[j].getTitle()) < 0)
else if ((a[i].getTitle()).compareTo(a[j].getTitle()) > 0)
none of them work.
/**
* Write a description of class MovieV3Tester here.
*
* @author (your name)
* @version (a version number or a date)
*/
public class MovieV3Tester
{
public static void main(String [] args)
{
MovieV3 [] movies = {new MovieV3 ("Avatar", 2009, "Fox"),
new MovieV3 ("Titanic", 1997, "Paramount"),
new MovieV3 ("Star Wars: The Force Awakens", 2015, "Disney"),
new MovieV3 ("Avengers: Infinity War", 2018, "Disney"),
new MovieV3 ("Jurassic World", 2015, "Universal"),
new MovieV3 ("Marvel's The Avengers", 2012, "Disney"),
new MovieV3 ("Furious 7", 2015, "Universal"),
new MovieV3 ("Avengers: Age of Ultron", 2015, "Disney"),
new MovieV3 ("Black Panther", 2018, "Disney"),
new MovieV3 ("Harry Potter and the Deathly Hallows Part 2", 2012, "Warner Brothers")
};
System.out.println("Original\n");
print(movies);
System.out.println("\nBy Title Ascending\n");
mergeTitle(movies, 0, (movies.length-1));
mergeTitle(movies, 0, (movies.length-1));
print(movies);
System.out.println("\nBy Year Ascending\n");
mergeYear(movies, 0, (movies.length-1));
print(movies);
}
public static void print(MovieV3 [] movies)
{
for(MovieV3 movie : movies)
{
System.out.println(movie.getTitle() + ", " + movie.getYear() + " by " + movie.getStudio());
}
}
public static void merge( MovieV3[] a, int low, int mid, int high, int compare)
{
MovieV3[] temp = new MovieV3[ high - low + 1 ];
int i = low, j = mid + 1, n = 0;
if(compare == 1)
{
while( i <= mid || j <= high )
{
if( i > mid )
{
temp[ n ] = a[ j ];
j++;
}
else if( j > high )
{
temp[ n ] = a[ i ];
i++;
}
else if( a[ i ].getYear() < a[ j ].getYear() )
{
temp[ n ] = a[ i ];
i++;
}
else
{
temp[ n ] = a[ j ];
j++;
}
n++;
}
}
else if(compare ==2)
{
while( i <= mid || j <= high )
{
if( i > mid )
{
temp[ n ] = a[ j ];
j++;
}
else if( j > high )
{
temp[ n ] = a[ i ];
i++;
}
else if((a[ j ].getTitle()).compareTo(a[i].getTitle())< 0)
{
temp[ n ] = a[ i ];
i++;
}
else
{
temp[ n ] = a[ j ];
j++;
}
n++;
}
}
else
{
while( i <= mid || j <= high )
{
if( i > mid )
{
temp[ n ] = a[ j ];
j++;
}
else if( j > high )
{
temp[ n ] = a[ i ];
i++;
}
else if( a[ i ].getYear() < a[ j ].getYear() )
{
temp[ n ] = a[ i ];
i++;
}
else
{
temp[ n ] = a[ j ];
j++;
}
n++;
}
}
for( int k = low ; k <= high ; k++ )
a[ k ] = temp[ k - low ];
} // end of merge
public static void mergeYear(MovieV3[] a, int low, int high)
{
if( low == high )
return;
int mid = ( low + high ) / 2;
mergeYear( a, low, mid ); // recursive call
mergeYear( a, mid + 1, high); // recursive call
//Debugging Statements
//uncomment to print the listings after each pass through the sort
//System.out.println("\nCurrent list");
//for(Movie h : a)
// if( h != null) System.out.printf("$%10.2f \n", h.getCost() );
merge( a, low, mid, high, 1);
}
public static void mergeTitle(MovieV3[] a, int low, int high)
{
if( low == high )
return;
int mid = ( low + high ) / 2;
mergeYear( a, low, mid ); // recursive call
mergeYear( a, mid + 1, high); // recursive call
//Debugging Statements
//uncomment to print the listings after each pass through the sort
//System.out.println("\nCurrent list");
//for(Movie h : a)
// if( h != null) System.out.printf("$%10.2f \n", h.getCost() );
merge( a, low, mid, high, 2);
}
public static MovieV3 [] insertionTitle(MovieV3[] source,int compare)
{
MovieV3[] dest = new MovieV3[ source.length ];
for( int i = 0 ; i < source.length ; i++ )
{
MovieV3 next = source[ i ];
int insertIndex = 0;
int k = i;
while( k > 0 && insertIndex == 0 )
{
if(compare == 1)
{
if( next.getTitle().compareTo( dest[k-1].getTitle() ) > 0 )
{
insertIndex = k;
}
else
{
dest[ k ] = dest[ k - 1 ];
}
}
else
{
if( next.getTitle().compareTo( dest[k-1].getTitle() ) < 0 )
{
insertIndex = k;
}
else
{
dest[ k ] = dest[ k - 1 ];
}
}
k--;
}
dest[ insertIndex ] = next;
//Debugging Statements
//uncomment to print the listings after each pass through the sort
//System.out.println("\nPass # " + i);
//for(MovieV3 h : dest)
// if( h != null) System.out.printf("%-15s \n", h.getCity() );
} // end of for
return dest;
}
}
Hopefully, it will eventually output the following
Avatar, 2009 by Fox, Avengers: Age of Ultron, 2015 by Disney, Avengers: Infinity War, 2018 by Disney, Black Panther, 2018 by Disney, Furious 7, 2015 by Universal, Harry Potter and the Deathly Hallows Part 2, 2012 by Warner Brothers, Jurassic World, 2015 by Universal, Marvel's The Avengers, 2012 by Disney, Star Wars: The Force Awakens, 2015 by Disney, Titanic, 1997 by Paramount
This program sorts ints just fine, it's the String sort that doesn't work.
