Merge Sort Algorithm

by Vijayaprasad 2010-01-28 16:06:32

/*
* @(#)MergeSortAlgorithm.java 1.0 95/06/23 Jason Harrison
*
* Copyright (c) 1995 University of British Columbia
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and without
* fee is hereby granted provided that this copyright notice
* appears in all copies. Please refer to the file "copyright.html"
* for further important copyright and licensing information.
*
* UBC MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. UBC SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*/

/**
* A merge sort demonstration algorithm
* SortAlgorithm.java, Thu Oct 27 10:32:35 1994
*
* @author Jason Harrison@cs.ubc.ca
* @version 1.1, 12 Jan 1998
*/
class MergeSortAlgorithm extends SortAlgorithm {
void sort(int a[], int lo0, int hi0) throws Exception {
int lo = lo0;
int hi = hi0;
pause(lo, hi);
if (lo >= hi) {
return;
}
int mid = (lo + hi) / 2;

/*
* Partition the list into two lists and sort them recursively
*/
sort(a, lo, mid);
sort(a, mid + 1, hi);

/*
* Merge the two sorted lists
*/
int end_lo = mid;
int start_hi = mid + 1;
while ((lo <= end_lo) && (start_hi <= hi)) {
pause(lo);
if (stopRequested) {
return;
}
if (a[lo] < a[start_hi]) {
lo++;
} else {
/*
* a[lo] >= a[start_hi]
* The next element comes from the second list,
* move the a[start_hi] element into the next
* position and shuffle all the other elements up.
*/
int T = a[start_hi];
for (int k = start_hi - 1; k >= lo; k--) {
a[k+1] = a[k];
pause(lo);
}
a[lo] = T;
lo++;
end_lo++;
start_hi++;
}
}
}

void sort(int a[]) throws Exception {
sort(a, 0, a.length-1);
}
}

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