user-0 提问: 求牛人优化快排算法，先谢谢了

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user: user-1
content: /*   *快排法；   *通过一次排序将数组分为独立的两部分，其中一部分的所用数据比另一部分都要小。   *然后再对两部分独立排序，递归进行。   */   void Quick(int str[],int i,int j)   {       int m,n,temp;       int k;       m=i;       n=j;       k=str[(m+n)/2];       do       {           while(str[m]<k&&m<j)               m++;           while(str[n]>k&&n>i)               n--;           if(m<=n)           {               temp=str[m];               str[m]=str[n];               str[n]=temp;               m++;               n--;           }       }while(m<=n);       if(m<j)           Quick(str,m,j);       if(n>i)           Quick(str,i,n);   }

user: user-2
content: 引用 5 楼 misskissC 的回复:快速排序的层次改进 :http://blog.csdn.net/misskissc/article/details/19246569排相等元素 is the last result

user: user-2
content: 快速排序的层次改进 :http://blog.csdn.net/misskissc/article/details/19246569

user: user-3
content: glibc中的代码，供参考  /* Copyright (C) 1991,1992,1996,1997,1999,2004 Free Software Foundation, Inc.    This file is part of the GNU C Library.    Written by Douglas C. Schmidt (schmidt@ics.uci.edu).     The GNU C Library is free software; you can redistribute it and/or    modify it under the terms of the GNU Lesser General Public    License as published by the Free Software Foundation; either    version 2.1 of the License, or (at your option) any later version.     The GNU C Library is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU    Lesser General Public License for more details.     You should have received a copy of the GNU Lesser General Public    License along with the GNU C Library; if not, write to the Free    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA    02111-1307 USA.  */  /* If you consider tuning this algorithm, you should consult first:    Engineering a sort function; Jon Bentley and M. Douglas McIlroy;    Software - Practice and Experience; Vol. 23 (11), 1249-1265, 1993.  */  #include <alloca.h> #include <limits.h> #include <stdlib.h> #include <string.h>  /* Byte-wise swap two items of size SIZE. */ #define SWAP(a, b, size)                            　　\ do                                                     \ {                                                      \     register size_t __size = (size);                　 \     register char *__a = (a), *__b = (b);            　\     do                                                 \     {                                                  \         char __tmp = *__a;                             \           *__a++ = *__b;                               \           *__b++ = __tmp;                              \     } while (--__size > 0);                            \ } while (0)  /* Discontinue quicksort algorithm when partition gets below this size.    This particular magic number was chosen to work best on a Sun 4/260. */ #define MAX_THRESH 4  /* Stack node declarations used to store unfulfilled partition obligations. */ typedef struct {     char *lo;     char *hi; } stack_node;  /* The next 4 #defines implement a very fast in-line stack abstraction. */ /* The stack needs log (total_elements) entries (we could even subtract log(MAX_THRESH)).    Since total_elements has type size_t, we get as upper bound for log (total_elements):    bits per byte (CHAR_BIT) * sizeof(size_t).  */ #define STACK_SIZE　　　　 (CHAR_BIT * sizeof(size_t)) #define PUSH(low, high)　 ((void) ((top->lo = (low)), (top->hi = (high)), ++top)) #define POP(low, high)　　((void) (--top, (low = top->lo), (high = top->hi))) #define STACK_NOT_EMPTY  (stack < top)   /* Order size using quicksort.  This implementation incorporates    four optimizations discussed in Sedgewick:     1. Non-recursive, using an explicit stack of pointer that store the       next array partition to sort.  To save time, this maximum amount       of space required to store an array of SIZE_MAX is allocated on the       stack.  Assuming a 32-bit (64 bit) integer for size_t, this needs       only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).       Pretty cheap, actually.     2. Chose the pivot element using a median-of-three decision tree.       This reduces the probability of selecting a bad pivot value and       eliminates certain extraneous comparisons.     3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving       insertion sort to order the MAX_THRESH items within each partition.       This is a big win, since insertion sort is faster for small, mostly       sorted array segments.     4. The larger of the two sub-partitions is always pushed onto the       stack first, with the algorithm then concentrating on the       smaller partition.  This *guarantees* no more than log (total_elems)       stack size is needed (actually O(1) in this case)! */  void _quicksort (void *const pbase, size_t total_elems, size_t size, __compar_d_fn_t cmp, void *arg) {     register char *base_ptr = (char *) pbase;      const size_t max_thresh = MAX_THRESH * size;      if (total_elems == 0)         /* Avoid lossage with unsigned arithmetic below.  */         return;      if (total_elems > MAX_THRESH)     {         char *lo = base_ptr;         char *hi = &lo[size * (total_elems - 1)];         stack_node stack[STACK_SIZE];         stack_node *top = stack;          PUSH (NULL, NULL);          while (STACK_NOT_EMPTY)         {             char *left_ptr;             char *right_ptr;              /* Select median value from among LO, MID, and HI. Rearrange                LO and HI so the three values are sorted. This lowers the                probability of picking a pathological pivot value and                skips a comparison for both the LEFT_PTR and RIGHT_PTR in                the while loops. */              char *mid = lo + size * ((hi - lo) / size >> 1);              if ((*cmp) ((void *) mid, (void *) lo, arg) < 0)                 SWAP (mid, lo, size);             if ((*cmp) ((void *) hi, (void *) mid, arg) < 0)                 SWAP (mid, hi, size);             else                 goto jump_over;             if ((*cmp) ((void *) mid, (void *) lo, arg) < 0)                 SWAP (mid, lo, size); jump_over:             ;              left_ptr  = lo + size;             right_ptr = hi - size;              /* Here's the famous ``collapse the walls'' section of quicksort.                Gotta like those tight inner loops!  They are the main reason                that this algorithm runs much faster than others. */             do             {                 while ((*cmp) ((void *) left_ptr, (void *) mid, arg) < 0)                     left_ptr += size;                  while ((*cmp) ((void *) mid, (void *) right_ptr, arg) < 0)                     right_ptr -= size;                  if (left_ptr < right_ptr)                 {                     SWAP (left_ptr, right_ptr, size);                     if (mid == left_ptr)                         mid = right_ptr;                     else if (mid == right_ptr)                         mid = left_ptr;                     left_ptr += size;                     right_ptr -= size;                 }                 else if (left_ptr == right_ptr)                 {                     left_ptr += size;                     right_ptr -= size;                     break;                 }             }             while (left_ptr <= right_ptr);              /* Set up pointers for next iteration.  First determine whether                left and right partitions are below the threshold size.  If so,                ignore one or both.  Otherwise, push the larger partition's                bounds on the stack and continue sorting the smaller one. */              if ((size_t) (right_ptr - lo) <= max_thresh)             {                 if ((size_t) (hi - left_ptr) <= max_thresh)                     /* Ignore both small partitions. */                     POP (lo, hi);                 else                     /* Ignore small left partition.*/                     lo = left_ptr;             }             else if ((size_t) (hi - left_ptr) <= max_thresh)                 /* Ignore small right partition.*/                 hi = right_ptr;             else if ((right_ptr - lo) > (hi - left_ptr))             {                 /* Push larger left partition indices. */                 PUSH (lo, right_ptr);                 lo = left_ptr;             }             else             {                 /* Push larger right partition indices. */                 PUSH (left_ptr, hi);                 hi = right_ptr;             }         }     }      /* Once the BASE_PTR array is partially sorted by quicksort the rest        is completely sorted using insertion sort, since this is efficient        for partitions below MAX_THRESH size. BASE_PTR points to the beginning        of the array to sort, and END_PTR points at the very last element in        the array (*not* one beyond it!). */  #define min(x, y) ((x) < (y) ? (x) : (y))      {         char *const end_ptr = &base_ptr[size * (total_elems - 1)];         char *tmp_ptr = base_ptr;         char *thresh = min(end_ptr, base_ptr + max_thresh);         register char *run_ptr;          /* Find smallest element in first threshold and place it at the            array's beginning.  This is the smallest array element,            and the operation speeds up insertion sort's inner loop. */          for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)             if ((*cmp) ((void *) run_ptr, (void *) tmp_ptr, arg) < 0)                 tmp_ptr = run_ptr;          if (tmp_ptr != base_ptr)             SWAP (tmp_ptr, base_ptr, size);          /* Insertion sort, running from left-hand-side up to right-hand-side.  */          run_ptr = base_ptr + size;         while ((run_ptr += size) <= end_ptr)         {             tmp_ptr = run_ptr - size;             while ((*cmp) ((void *) run_ptr, (void *) tmp_ptr, arg) < 0)                 tmp_ptr -= size;              tmp_ptr += size;             if (tmp_ptr != run_ptr)             {                 char *trav;                  trav = run_ptr + size;                 while (--trav >= run_ptr)                 {                     char c = *trav;                     char *hi, *lo; 　　　　　　　　　　　 for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)                         * hi = *lo;                     *hi = c;                 }             }         }     } }

user: user-4
content: 快速排序的分析与优化：http://blog.csdn.net/lisonglisonglisong/article/details/32982809

user: user-5
content: quickly sort喷了