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Mergesort.java
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Mergesort.java
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import java.util.Scanner;
public class Mergesort{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] a;
int i;
System.out.print("Enter the no.of elements of an array : ");
int n = input.nextInt();
a = new int[n];
System.out.println("Enter array elements : ");
for(i=0;i<n;i++){
a[i] = input.nextInt();
}
System.out.println("Before sorting............");
for(int j : a)
System.out.print(j+" ");
System.out.println();
merge(a,0,n-1);
System.out.println("After sorting............");
for(int j : a)
System.out.print(j+" ");
}
public static void merge(int[] a,int lb,int ub){
if(lb<ub){
int mid=(lb+ub)/2;
merge(a,lb,mid);
merge(a,mid+1,ub);
mergeSort(a,lb,mid,ub);
}
}
public static void mergeSort(int[] a,int lb,int mid,int ub){
int i = lb;
int j = mid+1;
int k=lb;
int[] b = new int[20];
while(i<=mid && j<=ub){
if(a[i]>=a[j]){
b[k] =a[j];
j++;
k++;
}
else{
b[k] = a[i];
i++;
k++;
}
}
while(j<=ub){
b[k]=a[j];
k++;j++;
}
while(i<=mid){
b[k]=a[i];
k++;i++;
}
for(int l=lb;l<=ub;l++)
a[l] = b[l];
}
}