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Sort Algorithm Fix

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- The sort algorithm (Combsort11) was broken because it didn't
  consider all the possible variations of present/missing, same/
  different combinations of data, when performing a compare.  This
  led to an unstable sort, which is an infinite loop in Combsort11.
This commit is contained in:
Paul Beckingham 2009-03-02 23:49:13 -05:00
parent 1e70400143
commit a1b7516cf8
1 changed files with 53 additions and 13 deletions
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66
src/Table.cpp
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@ -764,6 +764,32 @@ void Table::optimize (std::string& output)
////////////////////////////////////////////////////////////////////////////////
// Combsort11, with O(n log n) average, O(n log n) worst case performance.
//
// function combsort11(array input)
// gap := input.size
//
// loop until gap <= 1 and swaps = 0
// if gap > 1
// gap := gap / 1.3
// if gap = 10 or gap = 9
// gap := 11
// end if
// end if
//
// i := 0
// swaps := 0
//
// loop until i + gap >= input.size
// if input[i] > input[i+gap]
// swap(input[i], input[i+gap])
// swaps := 1
// end if
// i := i + 1
// end loop
//
// end loop
// end function
#define SWAP \
{ \
int temp = order[r]; \
@ -776,7 +802,7 @@ void Table::sort (std::vector <int>& order)
int gap = order.size ();
int swaps = 1;
while (gap > 1 || swaps != 0)
while (gap > 1 || swaps > 0)
{
if (gap > 1)
{
@ -797,10 +823,28 @@ void Table::sort (std::vector <int>& order)
Grid::Cell* left = mData.byRow (order[r], mSortColumns[c]);
Grid::Cell* right = mData.byRow (order[r + gap], mSortColumns[c]);
if (left == NULL && right != NULL)
SWAP
if (left && right && *left != *right)
// Data takes precedence over missing data.
if (left == NULL && right != NULL)
{
SWAP
break;
}
// No data - try comparing the next column.
else if (left == NULL && right == NULL)
{
keepScanning = true;
}
// Identical data - try comparing the next column.
else if (left && right && *left == *right)
{
keepScanning = true;
}
// Differing data - do a proper comparison.
else if (left && right && *left != *right)
{
switch (mSortOrder[mSortColumns[c]])
{
@ -861,24 +905,20 @@ void Table::sort (std::vector <int>& order)
break;
case ascendingPriority:
if (((std::string)*left == "" && (std::string)*right != "") ||
((std::string)*left == "M" && (std::string)*right == "L") ||
((std::string)*left == "H" && ((std::string)*right == "L" || (std::string)*right == "M")))
if (((std::string)*left == "" && (std::string)*right != "") ||
((std::string)*left == "M" && (std::string)*right == "L") ||
((std::string)*left == "H" && ((std::string)*right == "L" || (std::string)*right == "M")))
SWAP
break;
case descendingPriority:
if (((std::string)*left == "" && (std::string)*right != "") ||
if (((std::string)*left == "" && (std::string)*right != "") ||
((std::string)*left == "L" && ((std::string)*right == "M" || (std::string)*right == "H")) ||
((std::string)*left == "M" && (std::string)*right == "H"))
((std::string)*left == "M" && (std::string)*right == "H"))
SWAP
break;
}
break;
}
else
keepScanning = true;
}
++r;