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mergesort.c
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mergesort.c
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#include <stdio.h>
#define MIN -100000
#define MAX 100000
void mergesort(int*a,int low,int high);
void merge(int*a,int low,int mid,int high);
int main()
{
int i,j,n=6;
int a[]={6,5,4,3,2,1};
mergesort(a,0,5);
for(i=0;i<n;i++)
printf("%d ",a[i]);
}
void mergesort(int*a,int low,int high)
{
int i,mid;
if(low<high)
{
mid=(low+high)/2;
mergesort(a,low,mid);
mergesort(a,mid+1,high);
merge(a,low,mid,high);
}
}
void merge(int*a,int low,int mid,int high)
{
int i;
int j;
int k;
int l_len=mid-low+1,r_len=high-mid;
int l[l_len];
int r[r_len];
i=0;
for(k=low;k<=mid;k++)
{
l[i]=a[k];
i++;
}
j=0;
for(k=mid+1;k<=high;k++)
{
r[j]=a[k];
j++;
}
i=0;j=0;
for(k=low;k<=high;k++)
{
if(i<l_len && j<r_len)
{
if(l[i]<=r[j])
{
a[k]=l[i];
i++;
}
else
{
a[k]=r[j];
j++;
}
}
else if(i>=(l_len))
{
a[k]=r[j];
j++;
}
else if(j>=(r_len))
{
a[k]=l[i];
i++;
}
}
}