selectionSort.js

/*
SELECTION SORT

*** Description

Iterate over array and grow a sorted array behind current element.

For each position, find the smallest element in unsorted subarray starting at that position,
and swap elements so that smallest element is at the beginning of unsorted subarray.
*/
const selectionSort = function(array, comparator) {
    comparator = comparator || defaultComparator;
    array.forEach(function(element, index) {
        // for each position, find index of minimum value in subarray starting at that positions
        var minValue = element;
        var minIndex = index;
        for (var i = index; i < array.length; i++) {
            if (comparator(array[i], minValue) < 0) {
                minValue = array[i];
                minIndex = i;
            }
        }
        // swap values at min index and current position
        swap(array, index, minIndex);
    });
};

function swap(array, i1, i2) {
    let temp = array[i1];
    array[i1] = array[i2];
    array[i2] = temp;
}

function defaultComparator(a, b) {
    if (a < b) return -1; // a comes first
    else if (a > b) return 1; // b comes first
    return 0;
};

export default selectionSort