How to add a value in an array to the values before and after it

Question

I am trying to turn an array of numbers into steps of the value of the Non-Zero integer element i.e

spread([0,0,n,0,0] returns => 
[0 + n-2, 0 + n-1, n, 0 +         


        

Answer 1

Somehow "old-school", but seems to work:

let spread = a => {

    let add = a.map(_ => 0);

    a.forEach((x, i) => {
        for (let c = 1; x > 1 && c < a.length; c++, x--) {
            add[i + c] += x - 1;
            add[i - c] += x - 1;
        }
    });

    return a.map((x, i) => x + add[i]);
};

//

console.log(spread([0, 0, 0, 4, 0, 0, 0]).join())
console.log(spread([0, 0, 0, 3, 0, 2, 0]).join())
console.log(spread([3, 0, 0, 0, 0, 0]).join())