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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 sc = new Scanner(System.in);
System.out.print("Enter the number of elements : ");
int n = sc.nextInt();
int arr[] = new int[n];
System.out.println("Enter " + n + " elements :");
for (int i = 0; i < n; i++)
arr[i] = sc.nextInt();
mergeSort(arr, 0, n - 1);
System.out.println("\nThe sorted array : ;");
for (int i = 0; i < n; i++)
System.out.print(arr[i] + " ");
System.out.println();
}
static void mergeSort(int arr[], int lower, int upper) {
if (lower >= upper)
return;
int m = (lower + upper) / 2;
mergeSort(arr, lower, m);
mergeSort(arr, m + 1, upper);
merge(arr, lower, upper);
}
private static void merge(int arr[], int lower, int upper) {
int m = (lower + upper) / 2;
int a[] = new int[m - lower + 1];
int b[] = new int[upper - m];
int i, k = 0, k1 = 0, k2 = 0;
for (i = lower; i <= m; i++, k++)
a[k] = arr[i];
k = 0;
for (; i <= upper; i++, k++)
b[k] = arr[i];
for (i = lower; i <= upper && k1 < m - lower + 1 && k2 < upper - m; i++) {
if (a[k1] < b[k2]) {
arr[i] = a[k1];
k1++;
} else {
arr[i] = b[k2];
k2++;
}
}
for (; k1 < m - lower + 1; k1++)
arr[i++] = a[k1];
for (; k2 < upper - m; k2++)
arr[i++] = b[k2];
}
}