Selection sort (original) (raw)

Selection sort is a sort algorithm that works as follows:

remove the lowest datum one at a time until the set of data is empty

The naive algorithm, iterating through a list of n unsorted items, has a worst-case, average-case and best-case run-time of O(_n_2), assuming that comparisons can be done in constant time.

Heapsort optimizes the algorithm by using a heap data structure to speed up the finding and removing of the lowest datum.

Example

Here is a simple implementation of selection sort in C (from pd lecture notes):

int find_min_index (float [], int, int); void swap (float [], int, int); /* selection sort on array v of n floats */ void selection_sort (float v[], int n) {

int i;

/* for i from 0 to n-1, swap v[i] with the minimum

• of the i'th to the n'th array elements / for (i=0; i<n-1; i++)="" swap="" (v,="" i,="" find_min_index="" n));="" <="" pre="">} / find the index of the minimum element of float array v from

• indices start to end */

int find_min_index (float v[], int start, int end) {

int i, mini;

mini = start; for (i=start+1; i<end; i++)="" if="" (v[i]="" <="" v[mini])="" mini="i;" return="" mini;="" pre="">} /* swap i'th with j'th elements of float array v */ void swap (float v[], int i, int j) {

float t;

t = v[i]; v[i] = v[j]; v[j] = t;

} </end;>

</n-1;>