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sort.c

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#define NRANSI
#include "nrutil.h"
#define SWAP(a,b) temp=(a);(a)=(b);(b)=temp;
#define M 7
#define NSTACK 50

void sort(unsigned long n, float arr[])
{
        unsigned long i,ir=n,j,k,l=1;
        int jstack=0,*istack;
        float a,temp;

        istack=ivector(1,NSTACK);
        for (;;) {
                if (ir-l < M) {
                        for (j=l+1;j<=ir;j++) {
                                a=arr[j];
                                for (i=j-1;i>=1;i--) {
                                        if (arr[i] <= a) break;
                                        arr[i+1]=arr[i];
                                }
                                arr[i+1]=a;
                        }
                        if (jstack == 0) break;
                        ir=istack[jstack--];
                        l=istack[jstack--];
                } else {
                        k=(l+ir) >> 1;
                        SWAP(arr[k],arr[l+1])
                        if (arr[l+1] > arr[ir]) {
                                SWAP(arr[l+1],arr[ir])
                        }
                        if (arr[l] > arr[ir]) {
                                SWAP(arr[l],arr[ir])
                        }
                        if (arr[l+1] > arr[l]) {
                                SWAP(arr[l+1],arr[l])
                        }
                        i=l+1;
                        j=ir;
                        a=arr[l];
                        for (;;) {
                                do i++; while (arr[i] < a);
                                do j--; while (arr[j] > a);
                                if (j < i) break;
                                SWAP(arr[i],arr[j]);
                        }
                        arr[l]=arr[j];
                        arr[j]=a;
                        jstack += 2;
                        if (jstack > NSTACK) nrerror("NSTACK too small in sort.");
                        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

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