Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

This simple insertion–sort algorithm goes as follows. We start with the first
character in the array. One character by itself is already sorted. Then we consider
the next character in the array. If it is smaller than the first, we swap them. Next
we consider the third character in the array. We swap it leftward until it is in its
proper order with the first two characters. We then consider the fourth character,
and swap it leftward until it is in the proper order with the first three. We continue
in this manner with the fifth integer, the sixth, and so on, until the whole array is
sorted. Mixing this informal description with programming constructs, we can
express the insertion-sort algorithm as shown in Code Fragment 3.5.
Code Fragment 3.5: High-level description of the
insertion-sort algorithm.
This is a nice, high-level description of insertion-sort. It also demonstrates why
this algorithm is called "insertion-sort"—because each iteration of the main
inserts the next element into the sorted part of the array that comes before it.
Before we can code this description up, however, we need to work out more of
the details of how we do this insertion task.
Diving into those details a bit more, let us rewrite our description so that we now
use two nested loops. The outer loop will consider each element in the array in
turn and the inner loop will move that element to its proper location with the
(sorted) subarray of characters that are to its left.
Refining the Details for Insertion-Sort
Refining the details, then, we can describe our algorithm as shown in Code
Fragment 3.6.
Code Fragment 3.6: Intermediate-level description
of the insertion-sort algorithm.
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