// The challenge in this problem is in meeting its (arbitrary) constraints:

// Do not convert into strings or manipulate strings at all.
// Do not create any other data structures.
// In particular, don't instantiate a new array.
// The big-O of the solution should be O(n).
//a,e,i,o,u

//O(n^2) currently, in the case every letter is a vowel
let vowelDoubler = (vowelArray) => {
    for (let i = 0; i < vowelArray.length; i ++) {
        let letter = vowelArray[i];
        if (letter === 'a') {
            vowelArray.splice(i,0,letter);
            i++;
        }
        else if (letter === 'e') {
            vowelArray.splice(i,0,letter);
            i++;
        }
        else if (letter === 'i') {
            vowelArray.splice(i,0,letter);
            i++;
        }
        else if (letter === 'o') {
            vowelArray.splice(i,0,letter);
            i++;
        }
        else if (letter === 'u') {
            vowelArray.splice(i,0,letter);
            i++;
        }
    }
    return vowelArray;
};



//TESTING
let testArr = ['w','h','a','t',' ','o','n',' ','e','a','r','t','h',' ','a','r','e',' ','y','o','u',' ','t','a','l','k','i','n','g',' ','a','b','o','u','t','?'];
let testArrRes = ['w','h','a','a','t',' ','o','o','n',' ','e','e','a','a','r','t','h',' ','a','a','r','e','e',' ','y','o','o','u','u',' ','t','a','a','l','k','i','i','n','g',' ','a','a','b','o','o','u','u','t','?'];
let vowelArr = ['a', 'e', 'i', 'o', 'u'];