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99 lines
3.0 KiB
99 lines
3.0 KiB
/* qsort -- qsort interface implemented by faster quicksort. |
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J. L. Bentley and M. D. McIlroy, SPE 23 (1993) 1249-1265. |
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Copyright 1993, John Wiley. |
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*/ |
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typedef int cmp_t(const char *, const char *, unsigned int); |
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/*assume sizeof(long) is a power of 2 */ |
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#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \ |
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es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1; |
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#define swapcode(TYPE, parmi, parmj, n) { \ |
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register TYPE *pi = (TYPE *) (parmi); \ |
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register TYPE *pj = (TYPE *) (parmj); \ |
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do { \ |
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register TYPE t = *pi; \ |
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*pi++ = *pj; \ |
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*pj++ = t; \ |
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} while ((n -= sizeof(TYPE)) > 0); \ |
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} |
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#include <stddef.h> |
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static void swapfunc(char *a, char *b, size_t n, int swaptype) |
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{ if (swaptype <= 1) swapcode(long, a, b, n) |
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else swapcode(char, a, b, n) |
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} |
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#define swap(a, b) \ |
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if (swaptype == 0) { \ |
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t = *(long*)(a); \ |
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*(long*)(a) = *(long*)(b); \ |
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*(long*)(b) = t; \ |
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} else \ |
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swapfunc(a, b, es, swaptype) |
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#define vecswap(a, b, n) if (n > 0) swapfunc(a, b, n, swaptype) |
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#ifndef min |
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#define min(x, y) ((x)<=(y) ? (x) : (y)) |
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#endif |
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static char *med3(char *a, char *b, char *c, cmp_t *cmp, unsigned int flag) |
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{ return cmp(a, b, flag) < 0 ? |
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(cmp(b, c, flag) < 0 ? b : cmp(a, c, flag) < 0 ? c : a) |
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: (cmp(b, c, flag) > 0 ? b : cmp(a, c, flag) > 0 ? c : a); |
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} |
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void quicksort(char *a, size_t n, size_t es, cmp_t *cmp, unsigned flag) |
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{ |
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char *pa, *pb, *pc, *pd, *pl, *pm, *pn; |
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int r, swaptype; |
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long t; |
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size_t s; |
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loop: SWAPINIT(a, es); |
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if (n < 7) { /* Insertion sort on smallest arrays */ |
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for (pm = a + es; pm < a + n*es; pm += es) |
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for (pl = pm; pl > a && cmp(pl-es, pl, flag) > 0; pl -= es) |
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swap(pl, pl-es); |
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return; |
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} |
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pm = a + (n/2)*es; /* Small arrays, middle element */ |
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if (n > 7) { |
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pl = a; |
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pn = a + (n-1)*es; |
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if (n > 40) { /* Big arrays, pseudomedian of 9 */ |
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s = (n/8)*es; |
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pl = med3(pl, pl+s, pl+2*s, cmp, flag); |
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pm = med3(pm-s, pm, pm+s, cmp, flag); |
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pn = med3(pn-2*s, pn-s, pn, cmp, flag); |
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} |
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pm = med3(pl, pm, pn, cmp, flag); /* Mid-size, med of 3 */ |
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} |
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swap(a, pm); |
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pa = pb = a + es; |
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pc = pd = a + (n-1)*es; |
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for (;;) { |
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while (pb <= pc && (r = cmp(pb, a, flag)) <= 0) { |
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if (r == 0) { swap(pa, pb); pa += es; } |
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pb += es; |
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} |
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while (pb <= pc && (r = cmp(pc, a, flag)) >= 0) { |
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if (r == 0) { swap(pc, pd); pd -= es; } |
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pc -= es; |
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} |
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if (pb > pc) break; |
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swap(pb, pc); |
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pb += es; |
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pc -= es; |
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} |
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pn = a + n*es; |
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s = min(pa-a, pb-pa ); vecswap(a, pb-s, s); |
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s = min(pd-pc, pn-pd-(long)es); vecswap(pb, pn-s, s); |
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if ((s = pb-pa) > es) quicksort(a, s/es, es, cmp, flag); |
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if ((s = pd-pc) > es) { |
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/* Iterate rather than recurse to save stack space */ |
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a = pn - s; |
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n = s / es; |
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goto loop; |
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} |
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/* quicksort(pn-s, s/es, es, cmp, flag); */ |
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}
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