116 lines
3.4 KiB
Java
116 lines
3.4 KiB
Java
|
|
|
|
import edu.princeton.cs.introcs.StdIn;
|
|
import edu.princeton.cs.introcs.StdOut;
|
|
|
|
/*************************************************************************
|
|
* Compilation: javac InsertionX.java
|
|
* Execution: java InsertionX < input.txt
|
|
* Dependencies: StdOut.java StdIn.java
|
|
* Data files: http://algs4.cs.princeton.edu/21sort/tiny.txt
|
|
* http://algs4.cs.princeton.edu/21sort/words3.txt
|
|
*
|
|
* Sorts a sequence of strings from standard input using an optimized
|
|
* version of insertion sort.
|
|
*
|
|
* % more tiny.txt
|
|
* S O R T E X A M P L E
|
|
*
|
|
* % java InsertionX < tiny.txt
|
|
* A E E L M O P R S T X [ one string per line ]
|
|
*
|
|
* % more words3.txt
|
|
* bed bug dad yes zoo ... all bad yet
|
|
*
|
|
* % java InsertionX < words3.txt
|
|
* all bad bed bug dad ... yes yet zoo [ one string per line ]
|
|
*
|
|
*************************************************************************/
|
|
/**
|
|
* The InsertionX class provides static methods for sorting an
|
|
* array using an optimized version of insertion sort (with half exchanges
|
|
* and a sentinel).
|
|
*
|
|
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/21elementary">Section 2.1</a> of
|
|
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
|
|
*
|
|
* @author Robert Sedgewick
|
|
* @author Kevin Wayne
|
|
*/
|
|
|
|
public class InsertionX {
|
|
|
|
// This class should not be instantiated.
|
|
private InsertionX() { }
|
|
|
|
/**
|
|
* Rearranges the array in ascending order, using the natural order.
|
|
* @param a the array to be sorted
|
|
*/
|
|
public static void sort(Comparable[] a) {
|
|
int N = a.length;
|
|
|
|
// put smallest element in position to serve as sentinel
|
|
for (int i = N-1; i > 0; i--)
|
|
if (less(a[i], a[i-1])) exch(a, i, i-1);
|
|
|
|
// insertion sort with half-exchanges
|
|
for (int i = 2; i < N; i++) {
|
|
Comparable v = a[i];
|
|
int j = i;
|
|
while (less(v, a[j-1])) {
|
|
a[j] = a[j-1];
|
|
j--;
|
|
}
|
|
a[j] = v;
|
|
}
|
|
|
|
assert isSorted(a);
|
|
}
|
|
|
|
|
|
/***********************************************************************
|
|
* Helper sorting functions
|
|
***********************************************************************/
|
|
|
|
// is v < w ?
|
|
private static boolean less(Comparable v, Comparable w) {
|
|
return v.compareTo(w) < 0;
|
|
}
|
|
|
|
// exchange a[i] and a[j]
|
|
private static void exch(Object[] a, int i, int j) {
|
|
Object swap = a[i];
|
|
a[i] = a[j];
|
|
a[j] = swap;
|
|
}
|
|
|
|
|
|
/***********************************************************************
|
|
* Check if array is sorted - useful for debugging
|
|
***********************************************************************/
|
|
private static boolean isSorted(Comparable[] a) {
|
|
for (int i = 1; i < a.length; i++)
|
|
if (less(a[i], a[i-1])) return false;
|
|
return true;
|
|
}
|
|
|
|
// print array to standard output
|
|
private static void show(Comparable[] a) {
|
|
for (int i = 0; i < a.length; i++) {
|
|
StdOut.println(a[i]);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Reads in a sequence of strings from standard input; insertion sorts them;
|
|
* and prints them to standard output in ascending order.
|
|
*/
|
|
public static void main(String[] args) {
|
|
String[] a = StdIn.readAllStrings();
|
|
InsertionX.sort(a);
|
|
show(a);
|
|
}
|
|
|
|
}
|