The code runs for a small file size.But it hangs when i use a file of huge size say 100000.The code used is:
import java.util.Scanner;
import java.util.Formatter;
import java.util.NoSuchElementException;
import java.lang.IllegalStateException;
import java.io.FileNotFoundException;
import java.io.*;
import java.lang.*;
public class mergesort1
{
private int arr[];
private int length;
private Scanner sc;
private Formatter f;
public static int inversion=0;
public mergesort1()
{
try
{
sc=new Scanner(new File("IntegerArray.txt"));
}
catch(FileNotFoundException fe)
{
System.err.println("File not found");
}
arr=new int[100000];
length=arr.length;
int i=0;
try
{
while(sc.hasNext())
arr[i++]=sc.nextInt();
}
catch (NoSuchElementException ne)
{
System.err.println("File formed wrong");
sc.close();
System.exit(1);
}
catch(IllegalStateException stateException)
{
System.err.println("Error reading from the file.");
System.exit(1);
}
split(0,length-1);
writeback();
}
private void split(int low,int high)
{
int mid;
if ((high-low)>=1)
{
mid=(low+high)/2;
split(low,mid);
split(mid+1,high);
merge(low,mid+1,high);
}
}
private void merge(int low,int mid,int high)
{
int count=low;
int lcount=low;
int rcount=mid;
int[] merged=new int[length];
while (lcount<=mid-1 && rcount<=high)
{
if (arr[lcount]<arr[rcount])
merged[count++]=arr[lcount++];
else
{
merged[count++]=arr[rcount++];
inversion=inversion+(mid-1-low);
}
}
if (lcount!=mid)
{
while (lcount<=mid-1)
{
if (arr[count]!=count)
merged[count++]=arr[lcount++];
}
}
else
{
while (rcount<=high)
{
if (arr[count]!=count)
merged[count++]=arr[rcount++];
}
}
System.out.println("The inversions counted till now is "+inversion);
for(int i=low;i<=high;i++)
arr[i]=merged[i];
}
private void writeback()
{
try
{
f=new Formatter("output.txt");
}
catch(FileNotFoundException fe)
{
System.err.println("File Not found");
}
for(int i=0;i<arr.length;i++)
f.format("%d\n",arr[i]);
System.out.println("The number of inversions is:"+inversion);
sc.close();
f.close();
}
}
Now the code runs fine for a input of 2 4 1 3 5 and the number of inversions is 3.But for a code of counting inversions of a input of size:100000 it hangs after counting till 103782637.
