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10-40-11-02-16-06.10.c
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10-40-11-02-16-06.10.c
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/* 10-40-11-02-16-06.10.c -- 第十章第四十题 */
/* 02-18-01.54 完成.大概用了13小时. */
#include <stdio.h>
#include <stdlib.h>
#define FALSE (0)
#define TRUE (1)
typedef int Item ;
typedef int BOOL ;
/* Data is a kind of data structures. */
BOOL turnpike (Item * const points, const int size, Data * const distance) ;
BOOL place (Item * const points, const int size, const int left, const int right, Data * const distance) ;
Item absoluteValue (const Item value) ;
/* If it returns FLASE, points is no go. */
BOOL turnpike (Item * const points, const int size, Data * const distance)
{
Item max, temp ;
/* Set starting point. */
points[0] = 0 ;
max = FindMax (distance) ;
points[size - 1] = max ;
Delete (distance, max) ;
max = FindMax (distance) ;
points[size - 2] = max ;
Delete (distance, max) ;
temp = absoluteValue (points[size - 1] - points[size - 2]) ;
if (TRUE == Find (distance, temp))
{
Delete (distance, temp) ;
return place (points, size, 1, size - 3, distance) ;
}
else
return FALSE ;
}
BOOL place (Item * const points, const int size, const int left, const int right, Data * const distance)
{
BOOL found = FALSE, index = FALSE ;
Item max_in_distance, temp ;
int i, j, k ;
if (IsEmpty (distance))
return TRUE ;
max_in_distance = FindMax (distance) ;
/* Check if setting points[right] = DMax is feasible. */
/* Testing */
for (i = 0; i < left; i++)
{
temp = absoluteValue (points[i] - max_in_distance) ;
if (TRUE == Find (distance, temp))
Delete (distance, temp) ;
/* If hasn't found temp in distance. */
else
{
/* If has deleted. */
if (i > 0)
{
/* Recover the items that has been deleted. */
for (k = i - 1; k >= 0; k--)
{
temp = absoluteValue (points[k] - max_in_distance) ;
Insert (distance, temp) ;
}
}
/* To guide next step. */
index = TRUE ;
break ;
}
}
/* If has passed through the test on last step. */
if (FALSE == index)
{
/* Testing. */
for (j = right + 1; j < size; j++)
{
temp = absoluteValue (points[j] - max_in_distance) ;
if (TRUE == Find (distance, temp))
Delete (distance, temp) ;
/* If hasn't found temp in distance. */
else
{
/* If has deleted. */
if (j > right + 1)
{
/* Recover the items that has been deleted. */
for (k = j - 1; k > right; k--)
{
temp = absoluteValue (points[k] - max_in_distance) ;
Insert (distance, temp) ;
}
}
/* From points[i - 1] to points[0] has been deleted certainly. */
/* Recover the items that from points[i - 1] to points[0]. */
for (k = i - 1; k >= 0; k--)
{
temp = absoluteValue (points[k] - max_in_distance) ;
Insert (distance, temp) ;
}
/* To guide next step. */
index = TRUE ;
break ;
}
}
/* If has passed through the test on last step. */
if (FALSE == index)
{
/* Undoubted attempt. */
points[right] = max_in_distance ;
found = place (points, size, left, right - 1, distance) ;
/* Decide if go to backtrack. */
if (FALSE == found)
{
/* Backtrack. */
for (i = 0; i < left; i++)
{
temp = absoluteValue (points[i] - max_in_distance) ;
Insert (distance, temp) ;
}
for (i = right + 1; i < size; i++)
{
temp = absoluteValue (points[i] - max_in_distance) ;
Insert (distance, temp) ;
}
}
}
}
/* If first attempt failed, try to setting x[left] = x[N] - DMax is feasible. */
/* Decide if need this test. */
if (FALSE == found)
{
/* Initialize "index" again. */
index = FALSE ;
for (i = 0; i < left; i++)
{
/* Make sure you has known that temp is the absolute value of distance. */
temp = absoluteValue (points[size - 1] - max_in_distance - points[i]) ;
if (TRUE == Find (distance, temp))
Delete (distance, temp) ;
else
{
if (i > 0)
{
for (k = i - 1; k >= 0; k--)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[k]) ;
Insert (distance, temp) ;
}
}
index = TRUE ;
break ;
}
}
if (FALSE == index)
{
for (j = right + 1; j < size; j++)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[j]) ;
if (TRUE == find (distance, temp))
Delete (distance, temp) ;
else
{
if (j > right + 1)
{
for (k = j - 1; k > right; k--)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[k]) ;
Insert (distance, temp) ;
}
}
for (k = i - 1; k >= 0; k--)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[k]) ;
Insert (distance, temp) ;
}
index = TRUE ;
break ;
}
}
}
if (FALSE == index)
{
points[left] = points[size - 1] - max_in_distance ;
found = place (points, size, left + 1, right, distance) ;
if (FALSE == found)
{
/* Backtrack. */
for (i = 0; i < left; i++)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[i]) ;
Insert (distance, temp) ;
}
for (i = right + 1; i < size; i++)
{
temp = absoluteValue (points[size - 1] - max_in_distance - points[i]) ;
Insert (distance, temp) ;
}
}
}
}
return found ;
}
Item absoluteValue (const Item value)
{
if (value < 0)
return 0 - value ;
else
return value ;
}