public class MSort {

    // Merge Sort function
    public static void sort(int[] arr, int l, int r) {
        if (l < r) {
            int m = (l + r) / 2;
            sort(arr, l, m);
            sort(arr, m + 1, r);
            merge(arr, l, m, r);
        }
    }

    // Merge two parts
    public static void merge(int[] arr, int l, int m, int r) {
        int n1 = m - l + 1;
        int n2 = r - m;

        int[] left = new int[n1];
        int[] right = new int[n2];

        for (int i = 0; i < n1; i++)
            left[i] = arr[l + i];
        for (int j = 0; j < n2; j++)
            right[j] = arr[m + 1 + j];

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

        while (i < n1 && j < n2) {
            if (left[i] <= right[j]) {
                arr[k++] = left[i++];
            } else {
                arr[k++] = right[j++];
            }
        }

        while (i < n1)
            arr[k++] = left[i++];

        while (j < n2)
            arr[k++] = right[j++];
    }

    // Print array
    public static void show(int[] arr) {
        for (int num : arr)
            System.out.print(num + " ");
        System.out.println();
    }

    // Main method
    public static void main(String[] args) {
        int[] data = { 5, 2, 9, 1, 6, 3 };

        System.out.println("Before:");
        show(data);

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

        System.out.println("After:");
        show(data);
    }
}