I have a jagged array in ac# program that is declared where column one represents a year, column two represents the number of a month (1-12) and column three represents some data for that month:
double[][] data = new double[3][]
{
new double[] {1930,1931,1931,1931,1931,1931,1931,1931,1931,1931,1931,1931,1931,1932,1932,1932,1932,1932,1932,1932,1932,1932,1932,1932,1932},
new double[] {12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12},
new double[] {5, 6, 8, 3, 5, 8, 9, 6, 5, 6, 7, 5, 3, 2, 2, 2, 5, 7, 8, 3, 2, 2, 1, 2, 5}
};
As you can see, the first array is ordered. I would like to know how I could sort the jagged array by the second column , in ascending order like this.
{1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1931,1932,1930,1931,1932}
{1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 12}
etc...
My question is, how would I be able to implement this using an insertion sort. It needs to be a custom algorithm and cannot make use of the Array.Sort algorithm that comes as part of C#
Thanks
The insertion sort algorithm can easily be generalized (abstracted) to work on indexes by defining two functions - one to compare two indexes and one to swap two indexes, like this:
public static class Algorithms
{
public static void InsertionSort(int start, int count, Func<int, int, int> compare, Action<int, int> swap)
{
for (int i = start + 1, end = start + count; i < end; i++)
for (int j = i; j > start && compare(j - 1, j) > 0; j--)
swap(j - 1, j);
}
}
Now you can achieve your goal by comparing second columns and swap all columns like this:
Algorithms.InsertionSort(0, data[1].Length,
(a, b) => data[1][a].CompareTo(data[1][b]),
(a, b) => { foreach (var col in data) Algorithms.Swap(ref col[a], ref col[b]); });
where Algorithms.Swap
is another little helper:
public static void Swap<T>(ref T a, ref T b) { T c = a; a = b; b = c; }
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