75 Sort Colors

Problem Statement

Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

You must solve this problem without using the library's sort function.

Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]


BF: Would be two loops, first to create counts for each number, then second to overwrite array values.

Optimized: We have three pointers - i, low and high and are partitioning the array in three parts with the number 1 being the pivot point. In case of arr[i] being 2 we need to make sure to not increment i because the new element at index i (which was originally at the high index) hasn't been checked yet. For the other cases we increment the i index by one.

When I the current number is 0 I want to make sure that it will be moved to the low point, when the number is 2 I want to make sure that it will be moved to the high point.
When the number is 1 I don't care and move on.


var sortColors = function(arr) {
    let low = 0;
    let high = arr.length - 1;
    let i = 0;

    while (i <= high) {
        switch (arr[i]) {
            case 0:
                [arr[i], arr[low]] = [arr[low], arr[i]];
            case 1:
            case 2:
                [arr[i], arr[high]] = [arr[high], arr[i]];

    return arr;