Algorithm backup ---- Insertion Sort(插入排序算法)
Insertion sort is a simple sorting algorithm, a comparison sort in which the sorted array (or list) is built one entry at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort,heapsort or merge sort. However, insertion sort provides several advantages:
1. simple implementation
2. efficient for (quite) small data sets
3. adaptive, i.e. efficient for data sets that are already substantially sorted: the time compexity is O(n + d), where d is the number of inversions
4. more efficient in practice than most other simple quadratic (i.e. O(n2)) algorithms such as selection sort or bubble sort: the average running time is n2/4, and the running time is linear in the best case
5. stable, i.e. does not change the relative order of elements with equal keys
6. in-place, i.e. only requires a constant amount O(1) of additional memory space
7. online, i.e. can sort a list as it receives it.
Below is the implementation using C#:
/// Insertion sort algorithm
/// </summary>
/// <param name="numbers"> numbers array to be sorted </param>
public static void InsertionSort( int [] numbers)
{
for ( int i = 1 ; i < numbers.Length; ++ i)
{
int temp = numbers[i];
int j = i;
// Find its place and insert.
while (j > 0 && numbers[j - 1 ] >= temp)
{
numbers[j] = numbers[j - 1 ];
j -- ;
}
numbers[j] = temp;
}
}