排序算法--归并排序（merge）

 1 //merge-sort
 2 void merge(int *arry,const int first,const int mid,const int last)
 3 {
 4     int i,index;
 5     int first1,last1;
 6     int first2,last2;
 7     int *tmp;
 8     tmp=(int*)malloc((last-first+1)*sizeof(int));
 9     if (tmp==NULL)
10         return ;
11     first1=first;
12     last1=mid;
13     first2=mid+1;
14     last2=last;
15     index=0;
16     while((first1<=last1)&&(first2<=last2))
17     {
18         if (arry[first1]<arry[first2])
19         {
20             tmp[index++]=arry[first1];
21             first1++;
22         }
23         else{
24             tmp[index++]=arry[first2];
25             first2++;
26         }
27     }
28     while(first1<=last1)
29     {
30         tmp[index++]=arry[first1++];
31     }
32     while(first2<=last2)
33     {
34         tmp[index++]=arry[first2++];
35     }
36     for (i=0;i<last-first+1;i++)
37     {
38         arry[first+i]=tmp[i];
39     }
40     free(tmp);
41 }
42 
43 /*使用递归实现归并排序*/
44 void merge_sort(int *arry,const int first,const int last)
45 {
46     int mid=0;
47     if (first<last)
48     {
49         mid=(first+last)/2;
50         merge_sort(arry,first,mid);
51         merge_sort(arry,mid+1,last);
52         merge(arry,first,mid,last);
53     }
54 }

 1 /*** 使用迭代实现 ***/
 2 void merge_sort(int *list, const int first, const int last)
 3 {
 4     int len= last-first+1;
 5     int left_min,left_max;
 6     int right_min,right_max;
 7     int index;
 8     int i;
 9     int *tmp;
10     tmp = (int *)malloc(sizeof(int)*len);
11     if( tmp == NULL || len <= 0 )
12         return;
13     
14     for( i = 1; i < len; i *= 2 )
15     {
16         for( left_min = 0; left_min < len - i; left_min = right_max)
17         {
18             int j;
19             right_min = left_max = left_min + i;
20             right_max = left_max + i;
21             j = left_min;
22             if ( right_max > len )
23                 right_max = len;
24             index = 0;
25             while( left_min < left_max && right_min < right_max )
26             {
27                 tmp[index++] = (list[left_min] > list[right_min] ? list[right_min++] : list[left_min++]);
28             }
29             while( left_min < left_max )
30             {
31                 list[--right_min] = list[--left_max];
32             }
33             while( index > 0 )
34             {
35                 list[--right_min] = tmp[--index];
36             }
37             display_array(j,i*2,list+j);
38         }
39     }
40     free(tmp);
41 }

 1 int main()
 2 {
 3     int arry[]={1,2,5,6,4,7};
 4     merge_sort(arry,0,5);
 5     for (int i=0;i<6;i++)
 6     {
 7         cout<<arry[i]<<" ";
 8     }
 9     system("pause");
10     return 0;
11 }