suppose that we have three array

int a[]=new int[]{4,6,8,9,11,12};
int b[]=new int[]{3,5,7,13,14};
int c[]=new int[]{1,2,15,16,17};

and we want to merge it into one big d array where d.length=a.length+b.length+c.length
but we have memory problem it means that we must need use only this d array where we should merge these these three array of course we can use merge sort but can we use merge algorithm without sorting method? like two sorted array we can merge in one sorted array what about three or more array?