#include <iostream>
#include <stdlib.h> using namespace std;
int compared(const void *key1,const void *key2)
{
//cout<<"enter compare"<<endl;
const int* iKey1 = (int*)key1;
const int* iKey2 = (int*)key2;
//cout<<*iKey1<<endl;
//cout<<*iKey2<<endl; if(*iKey1>*iKey2){
//cout<<"big"<<endl;
return 1;
}
else if(*iKey1==*iKey2){
//cout<<"equal"<<endl;
return 0;
}
else if(*iKey1<*iKey2)
{
//cout<<"less"<<endl;
return -1;
}
} //k设置为size-1
//i设置为0
//j设置为中间数
static int merge(void* data, int esize, int i, int j, int k, int (*compare)
(const void* key1,const void* key2))
{
char *a = (char*)data, *m=NULL;
int ipos, jpos, mpos; ipos = i;
jpos = j+1;
mpos = 0; if((m=(char*)malloc(esize*((k-i)+1)))==NULL )
{
return -1;
} while(ipos<=j||jpos<=k)
{
if(ipos>j)
{
//the left elements has no more elements to merge
while(jpos<=k)
{
memcpy(&m[mpos*esize],&a[jpos*esize],esize);
jpos++;
mpos++;
}
continue;
}
else if(jpos>k)
{
//right division has no more elements to merge.
while(ipos<=j)
{
memcpy(&m[mpos*esize],&a[ipos*esize],esize);
ipos++;
mpos++;
}
continue;
}
if(compare(&a[ipos*esize],&a[jpos*esize])<0)
{
memcpy(&m[mpos*esize],&a[ipos*esize],esize);
ipos++;
mpos++;
}
else
{
memcpy(&m[mpos*esize],&a[jpos*esize],esize);
jpos++;
mpos++;
}
}
//prepare to merge data
memcpy(&a[i*esize], m,esize*((k-1)+1)); free(m); return 0; } int mgsort(void *data, int size, int esize, int i,int k,int (*compare)
(const void* key1,const void* key2))
{
int j;
//stop the recursion when no more element divisions can be made.
if(i<k)
{
//determine where to divide the elements
j = (int)(((i+k-1))/2); if(mgsort(data,size,esize,i,j,compared)<0)
{
return -1;
}
if(mgsort(data,size,esize,j+1,k,compared)<0)
{
return -1;
}
//merge the two sorted divisions into a single sorted set
if(merge(data,esize,i,j,k,compared)<0)
{
return -1;
}
}
return 0;
} int main(int argc, char *argv[])
{
int a[]={4,2,5,8,4,6}; for(int i=0;i<6;i++)
{
cout<<a[i]<<",";
}
cout<<endl; mgsort(a,6,4,0,5,compared); for(int i=0;i<6;i++)
{
cout<<a[i]<<",";
}
cout<<endl;
system("PAUSE");
return 0;
}