write a java program to sort unordered array numbers given u

write a java program to sort unordered array numbers (given) using three-way merge sort, by dividing the given array into 3 equal parts at each round

Solution

Answer:-

Merge Sort :

MergeSort is a Divide and Conquer algorithm. It divides input array in two halves, calls itself for the two halves and then merges the two sorted halves. The merge() function is used for merging two halves. The merge(arr, l, m, r) is key process that assumes that arr[l..m] and arr[m+1..r] are sorted and merges the two sorted sub-arrays into one.

Program :-

class MergeSort
{
// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
void merge(int arr[], int l, int m, int r)
{
// Find sizes of two subarrays to be merged
int n1 = m - l + 1;
int n2 = r - m;

/* Create temp arrays */
int L[] = new int [n1];
int R[] = new int [n2];

/*Copy data to temp arrays*/
for (int i=0; i<n1; ++i)
L[i] = arr[l + i];
for (int j=0; j<n2; ++j)
R[j] = arr[m + 1+ j];


/* Merge the temp arrays */

// Initial indexes of first and second subarrays
int i = 0, j = 0;

// Initial index of merged subarry array
int k = l;
while (i < n1 && j < n2)
{
if (L[i] <= R[j])
{
arr[k] = L[i];
i++;
}
else
{
arr[k] = R[j];
j++;
}
k++;
}

/* Copy remaining elements of L[] if any */
while (i < n1)
{
arr[k] = L[i];
i++;
k++;
}

/* Copy remaining elements of L[] if any */
while (j < n2)
{
arr[k] = R[j];
j++;
k++;
}
}

// Main function that sorts arr[l..r] using
// merge()
void sort(int arr[], int l, int r)
{
if (l < r)
{
// Find the middle point
int m = (l+r)/2;

// Sort first and second halves
sort(arr, l, m);
sort(arr , m+1, r);

// Merge the sorted halves
merge(arr, l, m, r);
}
}

/* A utility function to print array of size n */
static void printArray(int arr[])
{
int n = arr.length;
for (int i=0; i<n; ++i)
System.out.print(arr[i] + \" \");
System.out.println();
}

// Driver method
public static void main(String args[])
{
int arr[] = {12, 11, 13, 5, 6, 7};

System.out.println(\"Given Array\");
printArray(arr);

MergeSort ob = new MergeSort();
ob.sort(arr, 0, arr.length-1);

System.out.println(\"\ Sorted array\");
printArray(arr);
}
}