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#pragma once
/*
* Nicholas Noll (2020)
* Straight implementation of Sedgewick's median qsort
* #ref: "Implementing Quicksort Programs" (1978)
*
* @LEN: name of parameter length
* @QLESS: name of function that computes array[i] < array[j]
* should return a boolean
* @QSWAP: name of function that swaps array[i] <-> array[j]
* this could swap multiple arrays
*
* NOTE: This can perform on strided arrays.
* Make sure to use parens liberally to ensure hygeine!
*/
#define QSORT(LEN, QLESS, QSWAP) \
int i, j, m, r, l; \
struct { \
int i, j; \
} *sp, base[48]; \
sp = base; \
\
l = 1; \
r = LEN-1; \
\
if (LEN <= 14) goto ENDOUTER; \
OUTERLOOP: \
SWAP((l+r)/2, l+1); \
\
if (QLESS(r, l+1)) QSWAP(r, l+1); \
if (QLESS(r, l)) QSWAP(r, l); \
if (QLESS(l, l+1)) QSWAP(l, l+1); \
\
i = l+1; \
j = r; \
\
INNERLOOP: \
do ++i; while(QLESS(i, l)); \
do --j; while(QLESS(l, j)); \
if (j < i) goto ENDINNER; \
QSWAP(i, j); \
goto INNERLOOP; \
\
ENDINNER: \
QSWAP(l, j); \
\
if (MAX(j-l, r-i+1) <= 14) { \
if (sp == base) { \
goto ENDOUTER; \
} else { \
l = sp[-1].i; \
r = sp[-1].j; \
sp--; \
} \
} else { \
if (MIN(j-l, r-i+1) <= 14) { \
if (j-l > r-i+1) { \
l = l; \
r = j-1; \
} else { \
l = i; \
r = r; \
} \
} else { \
if (j-l > r-i+1) { \
sp->i = l; \
sp->j = j-1; \
sp++; \
\
l = i; \
r = r; \
} else { \
sp->i = i; \
sp->j = r; \
sp++; \
\
l = l; \
r = j-1; \
} \
} \
} \
goto OUTERLOOP; \
\
ENDOUTER: \
for (i = 1; i < LEN; i++) { \
for (j = i; j > 0 && QLESS(j, j-1); j--) { \
QSWAP(j, j-1); \
} \
} \
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