public class Sort {

    public static void main(String[] args) {
        int[] arr = {1, 4, 6, 2, 3, 4};

        merge(arr,0,arr.length-1);
        for (int i = 0; i < arr.length; i++) {
            System.out.print(i + " ");
        }
    }

    private static void merge(int[] arr, int left, int right) {
        if (left >= right) return;
        int mid = (left + right)/2;
        merge(arr,left,mid);
        merge(arr,mid+1,right);
        mergeTwo(arr,left,mid,right);
    }

    private static void mergeTwo(int[] a, int left, int mid, int right) {
        int[] tmp = new int[a.length];
        int r1 = mid + 1;
        int tIndex = left;
        while(left <=mid && r1 <= right) {
            if (a[left] <= a[r1])
                tmp[tIndex++] = a[left++];
            else
                tmp[tIndex++] = a[r1++];
        }

        while (left <=mid) {
            tmp[tIndex++] = a[left++];
        }

        while ( r1 <= right ) {
            tmp[tIndex++] = a[r1++];
        }
    }
}