10/06/2007

Insertion Sort

Algorithm AnalysisThe insertion sort works just like its name suggests - it inserts each item into its proper place in the final list. The simplest implementation of this requires two list structures - the source list and the list into which sorted items are inserted. To save memory, most implementations use an in-place sort that works by moving the current item past the already sorted items and repeatedly swapping it with the preceding item until it is in place.
Like the bubble sort, the insertion sort has a complexity of O(n2). Although it has the same complexity, the insertion sort is a little over twice as efficient as the bubble sort.
Pros: Relatively simple and easy to implement.Cons: Inefficient for large lists.
Source CodeBelow is the basic insertion sort algorithm.
void insertionSort(int numbers[], int array_size)
{
int i, j, index;
for (i=1; i < array_size; i++)
{
index = numbers[i];
j = i;
while ((j > 0) && (numbers[j-1] > index))
{
numbers[j] = numbers[j-1];
j = j - 1;
}
numbers[j] = index;
}
}

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