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#include <stdlib.h>
#ifdef MYDIR
#else
#include "TwoDView.h"
#include "TwoDTSP.h"
#include <appkit/graphics.h>
#endif
#include <math.h>
#include <limits.h>
#include <stdio.h>
#include "tspheaders.h"
#include "prototypes.h"
/************************************************************************/
/* This function implements the Nearest Neighbor Algorithm for the
Travelling Salesperson Algorithm. It provides an approximate optimal
value rather than the optimal value.
Reference: Lawler, Lenstra, et. al., The Traveling Salesman [sic] Problem,
1985, Wiley and Sons, p 150.
*/
/************************************************************************/
/* Parameters: TwoDView *self: Ye Old Drawing Object
float *Data: Pointer to the list of points.
Used to draw intermediate graph.
float *Distance: Pointer to area that contains the
Distances Between Each Pair of Cities
int *Tour: Pointer to area that will contain the
indices of the n arcs that are selected
to be a part of the tour
int NumberOfCities: Number of cities in the problem
*/
/************************************************************************/
/************************************************************************/
#ifdef MYDIR
float NearestNeighbor(float *Distance,int *Tour,int NumberOfCities) {
#else
float NearestNeighbor(TwoDView *self,float *data,float *Distance,int *Tour,
int NumberOfCities) {
#endif
int i,j,k,x,y,I,J,From,To,FirstCity,LastCity,MthCity,SubTourEnd,NewCity;
int *OnTour;
float ThisDistance,NewDistance,OptimalValue;
char msg[256];
/* allocate space for OnTour */
OnTour = (int *)malloc(NumberOfCities*sizeof(int));
if (OnTour == (int *) 0)
printf("Malloc for OnTour failed. \n");
for (i=0;i<NumberOfCities;i++) {
OnTour[i] = 0;
}
#ifdef DEBUGMYDIR
for (i=0;i<(NumberOfCities-1)*NumberOfCities/2;i++) {
printf("Distance[%d] = %f; \n",i,Distance[i]);
}
#endif
/* find the two cities with the minimum distance */
ThisDistance = ClosestCities(Distance,&From,&To,NumberOfCities);
/* if ThisDistance doesn't change, there is a problem ... */
if (ThisDistance == INT_MAX) {
printf("Error no initial subtour found. \n");
}
#ifdef DEBUGMYDIR
else {
printf("initial subtour \n");
printf("from %d to %d distance %f \n",From,To,ThisDistance);
}
#else
sprintf(msg,"from %d to %d distance %f \n",From,To,ThisDistance);
STATUS(msg);
#endif
/* given a subtour of m cities, add city m+1 closest to the mth city. */
/* OnTour indicates status of city
1 -- city is on tour
0 -- city is not yet on the tour */
Tour[0] = From;
Tour[1] = To;
OnTour[From] = OnTour[To] = 1;
FirstCity = From;
MthCity = To;
OptimalValue = ThisDistance;
SubTourEnd = 0;
NewDistance = INT_MAX;
NewCity = NumberOfCities;
/* keep adding cities until you include all NumberOfCities of them */
while (SubTourEnd < NumberOfCities-2) {
#ifdef DEBUGMYDIR
printf("Start of Iteration with %d cities in tour \n",SubTourEnd+1);
printf("MthCity is %d \n",MthCity);
#else
sprintf(msg,"%d cities in tour",SubTourEnd+1);
STATUS(msg);
#endif
/* look at all arcs starting at From */
I = ArcIndex(MthCity,NumberOfCities);
J = ArcIndex((MthCity+1),NumberOfCities);
for (i=I;i<J;i++) {
/* j = terminating end of this arc */
j = i-I+MthCity+1;
/* if the city at the other end isn't already on the tour ...*/
if (!OnTour[j]) {
/* Is the arc a new candidate for insertion? */
k = kfrom(MthCity,j,NumberOfCities);
ThisDistance = Distance[k];
if (ThisDistance < 0) {
printf("Error: ThisDistance = %f for MthCity %f j %f \n",MthCity,j);
}
if (ThisDistance < NewDistance) {
#ifdef DEBUGMYDIR
printf("Changing new city from %d to %d \n",NewCity,j);
printf("MthCity, j, %d %d \n",MthCity,j);
#else
sprintf(msg,"from %d to %d distance %f \n",From,To,ThisDistance);
STATUS(msg);
#endif
NewDistance = ThisDistance;
NewCity = j;
}
}
}
/* look at all arcs ending at MthCity */
for (i=0;i<MthCity;i++) {
/* if the starting city isn't already on the tour ...*/
if (!OnTour[i]) {
/* Is this arc a new candidate for insertion? */
k = kfrom(i,MthCity,NumberOfCities);
ThisDistance = Distance[k];
if (ThisDistance < 0) {
printf("Error: ThisDistance = %f for MthCity %f i %f \n",MthCity,i);
}
if (ThisDistance < NewDistance) {
#ifdef DEBUGMYDIR
printf("Changing cities from %d to %d \n",NewCity,i);
printf("MthCity, i, %d %d \n",MthCity,i);
#else
sprintf(msg,"Changing cities from %d to %d \n",NewCity,i);
STATUS(msg);
#endif
NewDistance = ThisDistance;
NewCity = i;
}
}
}
if (NewCity >= NumberOfCities) {
printf("Error: new city has not been found for tour. \n");
SubTourEnd = NumberOfCities;
OptimalValue = -1;
}
else {
/* add the new arc going from MthCity to NewCity to Tour */
#ifdef DEBUGMYDIR
printf("adding arc from %d to %d \n",MthCity,NewCity);
#endif
SubTourEnd+=1;
Tour[2*SubTourEnd] = MthCity;
Tour[2*SubTourEnd+1] = NewCity;
OnTour[NewCity] = 1;
/* update the Optimal Value */
OptimalValue+=NewDistance;
#ifdef DEBUGMYDIR
printf("adding %f to Opval to get %f \n",NewDistance,OptimalValue);
#else
sprintf(msg,"adding %f to Opval to get %f \n",NewDistance,OptimalValue);
STATUS(msg);
#endif
/* get ready to start at the top of the list again */
LastCity = NewCity;
MthCity = NewCity;
NewDistance = INT_MAX;
NewCity = NumberOfCities;
#ifdef DEBUGMYDIR
/* print out current subtour */
for (i=0;i<2*(SubTourEnd+1);i++) {
printf("i tour %d %d \n",i,Tour[i]);
}
#endif
#ifdef MYDIR
#else
/* draw the intermediate tour */
PSnewinstance();
for(i=0;i<2*(SubTourEnd+1);i+=2) {
x = Tour[i];
y = Tour[i+1];
[self drawEdge:X(x):Y(x):X(y):Y(y)];
}
NXPing();
[self->optimalValueField setFloatValue: OptimalValue at: 0];
usleep(self->drawTime);
#endif
}
}
/* add the final arc going from the first city to the last city */
SubTourEnd+=1;
Tour[2*SubTourEnd] = LastCity;
Tour[2*SubTourEnd+1] = FirstCity;
k = kfrom(FirstCity,LastCity,NumberOfCities);
#ifdef DEBUGMYDIR
printf("adding %f to Opval to get %f \n",Distance[k],OptimalValue);
#else
sprintf(msg,"adding %f to Opval to get %f \n",NewDistance,OptimalValue);
STATUS(msg);
#endif
OptimalValue = OptimalValue + Distance[k];
[self->optimalValueField setFloatValue: OptimalValue at: 0];
/* clean up */
free(OnTour);
/* return the optimal value */
return(OptimalValue);
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.