Given the complete factorization of a number, create a function that converts this array of factors to a string.
To illustrate: 24's complete factorization is [2, 2, 2, 3], which should be converted to "2^3 x 3".
stringFactor([2, 2, 2, 3, 3]) ➞ "2^3 x 3^2"
stringFactor([2, 7]) ➞ "2 x 7"
stringFactor([2, 3, 3]) ➞ "2 x 3^2"
x (multiplication sign).7 instead of 7^1.