Selection sort - Wikipedia, the free encyclopedia

selection sort is a sorting algorithm, specifically an in-place comparison sort. It has O(n²) time complexity, making it inefficient on large lists, and generally performs worse than the similar insertion sort. 

The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right at the front (left) of the list, and the sublist of items remaining to be sorted that occupy the rest of the list. The algorithm proceeds by finding the smallest (or largest, depending on sorting order) element in the unsorted sublist, exchanging it with the leftmost unsorted element (putting it in sorted order), and moving the sublist boundaries one element to the right.

/* a[0] to a[n-1] is the array to sort */
int i,j;
int iMin;
 
/* advance the position through the entire array */
/*   (could do j < n-1 because single element is also min element) */
for (j = 0; j < n-1; j++) {
    /* find the min element in the unsorted a[j .. n-1] */
 
    /* assume the min is the first element */
    iMin = j;
    /* test against elements after j to find the smallest */
    for ( i = j+1; i < n; i++) {
        /* if this element is less, then it is the new minimum */  
        if (a[i] < a[iMin]) {
            /* found new minimum; remember its index */
            iMin = i;
        }
    }
 
    /* iMin is the index of the minimum element */ 
    /* Swap it with the current position if the index of 
     * the smallest element is not already equal to the current index (j) 
     */
    if ( iMin != j ) {
        swap(a[j], a[iMin]);
    }
}

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