let think there are 5 slots in array index 1-5 !
after inserting 4 elements, you deleted 3 elements,
Now left ( used as front pointer ), points to arr[4]
again insert 4 elements, right ( used as rear pointer ) is points at arr[3].
Now for inserting one more element, arr[right+1] == Left, which indicates it is FULL.
PS :- we have to use mod technique, to rotate indices in loop !