Best way to create an array that goes 1-50 then 49-1 with only 1 loop

I know the best way to create an array that goes 1-50 then 49-1 would be 2 loops but this exercise requires us to use only 1 loop

    let myArr = [];
    let reachedFifty = false;
    let x = 1;

    for(i=0;i<100;i++){
        
        if(x == 50){
            reachedFifty = true;
        }

        myArr[i] = x;

        if(reachedFifty){
            x--;
        }
        else{
            x++;
        }
        
    }

This accomplished the task but the instructor said I’m using too much ifs and there are better solutions.

>Solution :

We can use the properties of the list to make this more efficient:

After filling the list with values it would look something like:

[1,2,3,4,.....,4,3,2,1]

We can see here that the list is symmetrical! By using this property, whenever we add a value on the "left" side, we can reflect it over to the right side:

let myArr = [];

for (let i = 0; i < 50; i++) {
  myArr[i] = i + 1;
  myArr[98 - i] = i + 1;
}

console.log(myArr)

.as-console-wrapper { max-height: 100% !important; }

Notice how we are using the index at 98 - i to reflect the changes across. This is because since there will be 99 total values, the value at index 0 should reflect to index 98, 1 to 97, etc.

I hope this helped answer your question! Please let me know if you need any further details or clarification 🙂