Review articles algorithms: insertion sort from theory to practice

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I. Introduction:

We learned in the previous chapter, the algorithm review articles: selection sort , this time we will continue to learn insertion sort

Second, the algorithm description

Brief (descending order): 1 ~ N one has to be sorted elements
Note: x behind said element or elements and the subscript y x or y sequence corresponding to the elements
1, take x (case x = 1) element as an element of the current to be compared;
2, so that y = x;
3, taken y-1 y element is compared with the element, if the element is greater than y-1 y position of the element, the element y and y-1 switching elements;
4, it is determined whether y is greater than 0, if greater than 0, execution continues to repeat step 3;
5, it is determined whether the x + 1 is greater than the length of the sequence, if not, the x = x + 1; we proceed to step 2, otherwise the end of the sort
As can be seen from the above, flashback sort feature is that the front element with the sort that have been sorted sequence of elements, so when x is equal to the last element of the sequence and when x sorted Hershey, at which time the sequence will Sort finished.

Third, code implementation

Code below, see the inside part of the code SortUtils algorithm review articles: Selection Sort :

class InsertSortDemo {
    fun sort(list: Array<Comparable<Any>>) {
        for (i in 1..(list.size - 1)) {
            var j = i;
            while (j > 0 && SortUtils.less(list[j], list[j - 1])) {
                SortUtils.exchange(list, j, j - 1);
                j--;
            }
        }
    }
}

Test code:

fun main(args: Array<String>) {
    var list: Array<String> = arrayOf("S", "O", "R","T", "E", "X","A","M","P","L","E");
    var insertSort = InsertSortDemo();
    var startTime = System.currentTimeMillis();
    insertSort.sort(list as Array<Comparable<Any>>)
    var endTime = System.currentTimeMillis();
    var costTime = endTime - startTime;
    println("花费时间： $costTime")
}

IV Summary:

Insertion Sort
Features: Elements of the left always order
Switching elements times: 0 is the lowest (the list is to be sorted list order) up to N ^ 2/2 times,
Average number of exchanges: N ^ 2/4 times
Comparison of the number of elements: preferably N-1 times (the list is to be sorted list order), the worst of N ^ 2/2 times the average of N ^ 2/4 times
More suitable for use in some scenarios insertion sort:
- 1, each element of the array a short distance from his final position, so that the number of comparisons and the number of exchanges are relatively small
- 2, only a few elements in the array of order

Review articles algorithms: insertion sort from theory to practice

I. Introduction:

Second, the algorithm description

Third, code implementation

IV Summary:

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