void merge_pass( float append[], int m, int n )
{
if( m!= n)
{
int mid = (m+n)/2;
merge_pass( append, m, mid );
merge_pass( append, mid+1, n );
merge_sort( append, m, mid, n );
}
}
void merge_sort( ElementType list[], int N )
{
ElementType extra[MAXN]; /* the extra space required */
int length = 1; /* current length of sublist being merged */
while ( length < N ) {
merge_pass( list, extra, N, length ); /* merge list into extra */
output( extra, N );
length *= 2;
merge_pass( extra, list, N, length ); /* merge extra back to list */
output( list, N );
length *= 2;
}
}
/*
* Run the full sort sequence.
*/
bool MergeSorter::sort()
{
// Get start time.
timeval start;
timeval end;
gettimeofday(&start, NULL);
// Create initial runs.
if (!create_runs()) {
fprintf(stderr, "Failed to create initial runs.\n");
return false;
}
// Now run the actual sort until run lengths are greater than or equal
// to number of record pages.
unsigned int pass = 0;
while (_run_length < _records_pages) {
// Switch input and output.
if (!swap_run_files()) {
return false;
}
// Now merge.
if (!merge_pass()) {
return false;
}
++pass;
}
// Now write out sorted.
if (fseek(_run_output, 0, SEEK_SET) != 0) {
fprintf(stderr, "Failed to move to start of output run.\n");
return false;
}
unsigned int count = _records_pages;
while (count != 0) {
// Read k + 1 pages at a time.
size_t records = fread(_pages, _page_size, _k + 1, _run_output);
if (records == 0) {
fprintf(stderr, "Failed to read page from output run.\n");
return false;
}
size_t written = fwrite(_pages, _page_size, records, _output);
if (written != records) {
fprintf(stderr, "Failed to write page to output.\n");
return false;
}
count -= written;
}
gettimeofday(&end, NULL);
int seconds = end.tv_sec - start.tv_sec;
int milliseconds = (end.tv_usec - start.tv_usec) / 1000;
printf("Successfully sorted in %u passes (not including original runs)!\n", pass);
printf("Took %d.%d seconds.\n", seconds, milliseconds);
return true;
}
void Arr<Type, Size>::merge(Type *out, Type *a, int s) {
if (s >= 1) {
int i = 0;
for (i=0; i+s<size; i += 2*s) {
int end = i+2*s > size ? size : i+2*s;
merge_pass(out, a, i, end, s);
}
copy(out, a, i, i, size-i);
}
}
void merge_sort(int * arr, int size)
{
int i;
int * temp_arr = NULL;
temp_arr = malloc(size * sizeof(int));
if (temp_arr == NULL)
{
fprintf(stderr, "Error: Memory allocation failed\n");
exit(1);
}
i=1;
for (i=1; i<size; i *= 4)
{
merge_pass(temp_arr, arr, size, i);
merge_pass(arr, temp_arr, size, i*2);
}
free(temp_arr);
}
/*
* 非递归调用
*/
void
merge_sort_v2(int a[], int n)
{
int b[n];
int i, gap;
/* 复制数组a为临时数组b */
for (i = 0; i < n; ++i)
b[i] = a[i];
gap = 1;
/* 两两循环归并 */
while (gap < n) {
merge_pass(a, b, gap, n);
gap *= 2;
}
}
void main()
{
float list[1000];
int i, n = 30;
printf("\n Size of the list: %d", n);
for(i = 0 ; i < n ; i++)
{
list[i] = (float) (rand() %100);
}
printf("\n Entered list as follows:\n");
for( i = 0 ; i<n ; i++)
printf(" %d ", (int) list[i]);
i = 0 ;
merge_pass(list, i, n-1);
printf("\n Merge sorted list is as follows:\n");
for( i = 0 ; i<n ; i++)
printf(" %d", (int) list[i]);
}
