package Arrays;

​

import java.util.Arrays;

​

public class MergeSort {

    static void sort(int[] arr) {

        if (arr.length < 2) return;

​

        int mid = arr.length / 2;

​

        int[] left_half = new int[mid];

        int[] right_half = new int[arr.length - mid];

​

        // copying the elements of array into left_half

        for (int i = 0; i < mid; i++) {

            left_half[i] = arr[i];

        }

        // copying the elements of array into right_half

        for (int i = mid; i < arr.length; i++) {

            right_half[i - mid] = arr[i];

        }

​

        sort(left_half);

        sort(right_half);

        merge(arr, left_half, right_half);

    }

    static void merge(int[] arr, int[] left_half, int[] right_half) {

        int i = 0, j = 0, k = 0;

​

        while (i < left_half.length && j < right_half.length) {

            if (left_half[i] < right_half[j]) {

                arr[k++] = left_half[i++];

            }

            else {

                arr[k++] = right_half[j++];

            }

        }

        while (i < left_half.length) {

            arr[k++] = left_half[i++];

        }

        while (j < right_half.length) {

            arr[k++] = right_half[j++];

        }

    }

    public static void main(String[] args) {

        int[] arr = {5, 1, 7, 3, 8, 0, 1, 5, 7, 2, 8, 9, -7, 4, -9, -3, 4};

        sort(arr);

        System.out.println(Arrays.toString(arr));

    }

}

public class MergeSort {

    public static void mergeSort(int[] arr) {

        if (arr == null || arr.length <= 1) {

            return; // Array is already sorted or empty

        }

​

        int[] temp = new int[arr.length];

        mergeSort(arr, temp, 0, arr.length - 1);

    }

​

    private static void mergeSort(int[] arr, int[] temp, int left, int right) {

        if (left < right) {

            int mid = left + (right - left) / 2;

​

            mergeSort(arr, temp, left, mid); // Sort the left half

            mergeSort(arr, temp, mid + 1, right); // Sort the right half

​

            merge(arr, temp, left, mid, right); // Merge the two sorted halves

        }

    }

​

    private static void merge(int[] arr, int[] temp, int left, int mid, int right) {

        for (int i = left; i <= right; i++) {

            temp[i] = arr[i];

        }

​

        int i = left;

        int j = mid + 1;

        int k = left;

​

        while (i <= mid && j <= right) {

            if (temp[i] <= temp[j]) {

                arr[k] = temp[i];

                i++;

            } else {

                arr[k] = temp[j];

                j++;

            }

            k++;

        }

​

        while (i <= mid) {

            arr[k] = temp[i];

            i++;

            k++;

        }

    }

​

    public static void main(String[] args) {

        int[] arr = {9, 5, 1, 3, 8, 4, 2, 7, 6};

        mergeSort(arr);

​

        System.out.println("Sorted array:");

        for (int num : arr) {

            System.out.print(num + " ");

        }

    }

}

public class MergeSort

{

public static void main(String[] args)

{

int i;

int values[] = new int[11];

for(i=0; i<values.length; i++) { values[i]=values.length-i; }

print(values);

sort(values,0,values.length-1);

print(values);

}

public static void sort(int[] numbers, int p,int r)

{

int q;

if(p<r)

{

q = (p+r)/2;

sort(numbers,p,q);

sort(numbers,q+1,r);

merge(numbers,p,q,r);

}

}

/**

* p, mid, and r are indices into the array such that p <= mid < r.

* The procedure assumes that the subarrays 'numbers[p..mid]' and 'numbers[mid+1..r]' are

* in sorted order. It merge them to form a single sorted subarray that replaces

* the current subarray 'numbers[p..r]'.

*/

private static void merge(int[] values, int p, int mid, int r)

{

int i,j,k;

int n1 = mid - p + 1;

int n2 = r - mid;

int[] left = new int[n1+1];

int[] right = new int[n2+1];

for(i=0; i<n1; i++)

{

left[i] = values[ p + i ];

}

for(j=0; j<n2; j++)

{

right[j] = values[mid + j + 1];

}

left[n1] = Integer.MAX_VALUE;

right[n2] = Integer.MAX_VALUE;

i=0; j=0;

for(k=p; k<=r; k++)

{

if(left[i]<=right[j])

{

values[k] = left[i];

i = i + 1;

}

else

{

values[k] = right[j];

j = j + 1;

}

}

}

public static void print(int[] numbers)

{

int i;

for(i=0; i<numbers.length; i++)

{

System.out.print(numbers[i]+ " ");

}

System.out.println();

}

}