I'm learning data structures from "Fundamentals of Data structures in C" by Sahni . In the topic, Circular Queue using Dynamic Array, the author has mentioned below point,
Let capacity be the initial capacity of the circular queue,We must first increase the size of the array using realloc,this will copy maximum of capacity elements on to the new array. To get a proper circular queue configuration, we must slide elements in the right segment(i.e, elements A and B) to the right end of the array(refer diagram 3.7.d). The array doubling and the slide to the right together copy at most 2 * capacity -2 elements.