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InsertionSort.js
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62 lines (56 loc) · 2.06 KB
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/* In insertion sort, we divide the initial unsorted array into two parts;
* sorted part and unsorted part. Initially the sorted part just has one
* element (Array of only 1 element is a sorted array). We then pick up
* element one by one from unsorted part; insert into the sorted part at
* the correct position and expand sorted part one element at a time.
*/
export function insertionSort(unsortedList) {
const len = unsortedList.length
for (let i = 1; i < len; i++) {
let j
const tmp = unsortedList[i] // Copy of the current element.
/* Check through the sorted part and compare with the number in tmp. If large, shift the number */
for (j = i - 1; j >= 0 && unsortedList[j] > tmp; j--) {
// Shift the number
unsortedList[j + 1] = unsortedList[j]
}
// Insert the copied number at the correct position
// in sorted part.
unsortedList[j + 1] = tmp
}
}
/**
* @function insertionSortAlternativeImplementation
* @description InsertionSort is a stable sorting algorithm
* @param {Integer[]} array - Array of integers
* @return {Integer[]} - Sorted array
* @see [InsertionSort](https://en.wikipedia.org/wiki/Quicksort)
*/
/*
* Big-O Analysis
* Time Complexity
- O(N^2) on average and worst case scenario
- O(N) on best case scenario (when input array is already almost sorted)
* Space Complexity
- O(1)
*/
export function insertionSortAlternativeImplementation(array) {
const length = array.length
if (length < 2) return array
for (let i = 1; i < length; i++) {
// Take current element in array
const currentItem = array[i]
// Take index of previous element in array
let j = i - 1
// While j >= 0 and previous element is greater than current element
while (j >= 0 && array[j] > currentItem) {
// Move previous, greater element towards the unsorted part
array[j + 1] = array[j]
j--
}
// Insert currentItem number at the correct position in sorted part.
array[j + 1] = currentItem
}
// Return array sorted in ascending order
return array
}