Mauritus national flag problem

Question

I\'ve made a solution for the Dutch national flag problem already.

But this time, I want to try something more difficult: the Mauritus national flag problem - 4 colours,

Answer 1

function sort3(a:string[]):void{
    let low = 0;
    let mid1 = 0;
    let mid2 = 0;
    let high = a.length - 1;
    while(mid2<=high){
        switch(a[mid2]){
            case '0': [a[mid2],a[low]] = [a[low],a[mid2]];
                    low++;
                    if(mid1