Insertion sort is a very intuitive algorithm as humans use this pattern naturally when sorting cards in our hands.

In this lesson, using TypeScript / Javascript, we’ll cover how to implement this algorithm, why this algorithm gets its name, and the complexity of our implementation of the insertion algorithm.

 

/** * ary: [4,3,2,1] *  * i = 1:  * current 3 * j = 0 --> array[j + 1] = array[j] --> [4, 4] * j = -1 --> array[j + 1] = current -->[3, 4] *  * i = 2:  * current: 2 * j = 1 --> array[j + 1] = array[j] --> [3,4,4] * j = 0 --> array[j + 1] = array[j] --> [3,3,4] * j = -1 --> array[j + 1] = current --> [2,3,4] */

 

function insertionSort(ary) {  let array = ary.slice();  for (let i = 1; i < array.length; i++) {    let current = array[i];    let j = i - 1;    while (j >= 0 && array[j] > current) {      // move the j to j+1      array[j + 1] = array[j];      j--;    }    // j = -1    array[j + 1] = current;  }  return array;}