我正在编写一个用于分配的程序，但是当我尝试使合并排序适用于String（按字母顺序排序）时，它将生成看似随机的标题顺序，如下所示。不久前我问了这个问题，但没有得到真正的答案，所以我觉得我需要用更好的措词并包括完整的代码。
按标题升序
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
我必须使用自己编写的合并排序来按字母顺序排列，并且在尝试了compareTo语句的各种不同配置后，例如：
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)
它们都不起作用。
/**
* 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;
}
}
希望它最终将输出以下内容
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
该程序对int进行排序就很好了，这是String排序不起作用的原因。
答案 0 :(得分：0)
您的大多数程序都是正确的；只有一些小错误。
这是您的代码版本，其中包含一些小的修正和注释：
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));
// Removed extra unnecessary call to `mergeTitle()`
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;
// Changed from `compare == 1` to this so that the last `else` block could be
// removed, as it was identical to this first block
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[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++;
}
// Changed the operator from `<` to `>` so that the titles are printed
// the way you showed in your post
else if ((a[j].getTitle()).compareTo(a[i].getTitle()) > 0)
{
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
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;
// I'm not sure if it was just a typo but in your code you had called `mergeYear()`
// twice instead of `mergeTitle()`, which was causing the sorting to not work
mergeTitle(a, low, mid); // recursive call
mergeTitle(a, mid + 1, high); // recursive call
merge(a, low, mid, high, 2);
}
}
即使所做的修改很小，并且您基本上已安装了正确的代码，但希望能有所帮助。
答案 1 :(得分：0)
mergeTitle方法中的一个小错误
public static void mergeTitle(MovieV3[] a, int low, int high)
{
....
mergeYear( a, low, mid ); // recursive call
^^^^^^^^^^^^^^^^^^^^^^^^ -> should be mergeTitle
mergeYear( a, mid + 1, high); // recursive call
^^^^^^^^^^^^^^^^^^^^^^^^ -> should be mergeTitle
....
merge( a, low, mid, high, 2);
}