快速排序

  1 #include <stdio.h>
  2 
  3 #define CUTOFF 3
  4 
  5 typedef int ElementType;
  6 
  7 void SwapTwoNum(ElementType *Num_1,ElementType *Num_2)
  8 {
  9     int NumTemp = *Num_1;
 10     *Num_1 = *Num_2;
 11     *Num_2 = NumTemp;
 12 }
 13 
 14 // Return Median of left,center,and right
 15 //order these and hide the pivot
 16 ElementType Median3(ElementType *Array,int Left,int Right)
 17 {
 18     int Center = (Left + Right) / 2;
 19     
 20     // C >= L,R >= L,R >= C ---> L <= C <= R
 21     if(Array[Left] > Array[Center])
 22     {
 23         SwapTwoNum(&Array[Left],&Array[Center]);
 24     }
 25     if(Array[Left] > Array[Right])
 26     {
 27         SwapTwoNum(&Array[Left],&Array[Right]);
 28     }
 29     if(Array[Center] > Array[Right])
 30     {
 31         SwapTwoNum(&Array[Center],&Array[Right]);
 32     }
 33     
 34     //Hide pivot
 35     SwapTwoNum(&Array[Center],&Array[Right-1]);
 36     return Array[Right-1];
 37 }
 38 
 39 void InsertionSort(ElementType *Array,int ArrayLen)
 40 {
 41     int i,j;
 42     ElementType ExtractElem;
 43     for(i = 1;i < ArrayLen;i ++)
 44     {
 45         ExtractElem = Array[i];
 46         for(j = i;j > 0 && ExtractElem < Array[j-1];j --)
 47         {
 48             Array[j] = Array[j-1];
 49         }
 50         //Insert
 51         Array[j] = ExtractElem;
 52     }
 53 }
 54 
 55 void QSort(ElementType *Array,int Left,int Right)
 56 {
 57     int i,j;
 58     ElementType Pivot;
 59     
 60     if(Left + CUTOFF <= Right)
 61     {
 62         Pivot = Median3(Array,Left,Right);
 63         i = Left;j = Right - 1;
 64         while(1)
 65         {
 66             while(Array[++i] < Pivot)
 67                 ;
 68             while(Array[--j] > Pivot)
 69                 ;
 70             if(i < j)
 71             {
 72                 SwapTwoNum(&Array[i],&Array[j]);
 73             }
 74             else
 75             {
 76                 break;
 77             }
 78         }
 79         
 80         //restore pivot
 81         SwapTwoNum(&Array[i],&Array[Right-1]);
 82         
 83         QSort(Array,Left,i-1);
 84         QSort(Array,i+1,Right);
 85     }
 86     else
 87     {
 88         InsertionSort(Array+Left,Right-Left+1);
 89     }
 90 }
 91 
 92 void QuickSort(ElementType *Array,int ArrayLen)
 93 {
 94     QSort(Array,0,ArrayLen-1);
 95 }
 96 
 97 int main()
 98 {
 99     ElementType TestArray[10] = {718,224,3332,4443,55,31,66,79,90,7};
100     QuickSort(TestArray,10);
101     int i;
102     for(i = 0;i < 10;i ++)
103     {
104         printf("%d ",TestArray[i]);
105     }
106     printf("\n");
107     return 0;
108 }