73 lines
1.4 KiB
C
73 lines
1.4 KiB
C
|
|
#define NRANSI
|
|
#include "nrutil.h"
|
|
#define SWAP(a,b) itemp=(a);(a)=(b);(b)=itemp;
|
|
#define M 7
|
|
#define NSTACK 50
|
|
|
|
void indexx(unsigned long n, float arr[], unsigned long indx[])
|
|
{
|
|
unsigned long i,indxt,ir=n,itemp,j,k,l=1;
|
|
int jstack=0,*istack;
|
|
float a;
|
|
|
|
istack=ivector(1,NSTACK);
|
|
for (j=1;j<=n;j++) indx[j]=j;
|
|
for (;;) {
|
|
if (ir-l < M) {
|
|
for (j=l+1;j<=ir;j++) {
|
|
indxt=indx[j];
|
|
a=arr[indxt];
|
|
for (i=j-1;i>=l;i--) {
|
|
if (arr[indx[i]] <= a) break;
|
|
indx[i+1]=indx[i];
|
|
}
|
|
indx[i+1]=indxt;
|
|
}
|
|
if (jstack == 0) break;
|
|
ir=istack[jstack--];
|
|
l=istack[jstack--];
|
|
} else {
|
|
k=(l+ir) >> 1;
|
|
SWAP(indx[k],indx[l+1]);
|
|
if (arr[indx[l]] > arr[indx[ir]]) {
|
|
SWAP(indx[l],indx[ir])
|
|
}
|
|
if (arr[indx[l+1]] > arr[indx[ir]]) {
|
|
SWAP(indx[l+1],indx[ir])
|
|
}
|
|
if (arr[indx[l]] > arr[indx[l+1]]) {
|
|
SWAP(indx[l],indx[l+1])
|
|
}
|
|
i=l+1;
|
|
j=ir;
|
|
indxt=indx[l+1];
|
|
a=arr[indxt];
|
|
for (;;) {
|
|
do i++; while (arr[indx[i]] < a);
|
|
do j--; while (arr[indx[j]] > a);
|
|
if (j < i) break;
|
|
SWAP(indx[i],indx[j])
|
|
}
|
|
indx[l+1]=indx[j];
|
|
indx[j]=indxt;
|
|
jstack += 2;
|
|
if (jstack > NSTACK) nrerror("NSTACK too small in indexx.");
|
|
if (ir-i+1 >= j-l) {
|
|
istack[jstack]=ir;
|
|
istack[jstack-1]=i;
|
|
ir=j-1;
|
|
} else {
|
|
istack[jstack]=j-1;
|
|
istack[jstack-1]=l;
|
|
l=i;
|
|
}
|
|
}
|
|
}
|
|
free_ivector(istack,1,NSTACK);
|
|
}
|
|
#undef M
|
|
#undef NSTACK
|
|
#undef SWAP
|
|
#undef NRANSI
|