## Problem Explanation

- Quick sort is an efficient sorting algorithm. It’s an in-place algorithm so it doesn’t take any auxilary space.
- First pick a random pivot point around which move all the smaller elements to it to the left of it and the bigger elements to the right of it.
- After getting the pivotIndex which is essentially the fixed position of that element, we find other pivotIndex by recusirvely calling this function.
- Quick sort’s worst case is
**O(n**^{2}) but that can be avoided if we pick random pivot point, so that way it’s big O is **O(nlogn)**.
- It’s space complexity is
**O(logn)**.
- It’s an
**unstable** algorithm.

## Solutions

## Solution 1 (Click to Show/Hide)

```
//Swapping array elements via ES6 array destructuring
function swap(arr, x, y) {
[arr[x], arr[y]] = [arr[y], arr[x]];
}
//Pivot function returns the fixed pivot point
function pivot(arr, left = 0, right = arr.length - 1) {
let shift = left;
for (let i = left + 1; i <= right; i++) {
//Move all the small elements on the left side
if (arr[i] < arr[left]) swap(arr, i, ++shift);
}
//Finally swapping the last element with the left
swap(arr, left, shift);
return shift;
}
function quickSort(array, left = 0, right = array.length - 1) {
if (left < right) {
let pivotIndex = pivot(array, left, right);
//Recusrively calling the function to the left of the pivot and to the right of the pivot
quickSort(array, left, pivotIndex - 1);
quickSort(array, pivotIndex + 1, right);
}
return array;
}
```

#### Relevant Links