Neutralisation

Given two strings comprised of + and -, return a new string which shows how the two strings interact in the following way:

• When positives and positives interact, they remain positive.
• When negatives and negatives interact, they remain negative.
• But when negatives and positives interact, they become neutral, and are shown as the number 0.

Worked Example

neutralise("+-+", "+--") ➞ "+-0"
// Compare the first characters of each string, then the next in turn.
// "+" against a "+" returns another "+".
// "-" against a "-" returns another "-".
// "+" against a "-" returns "0".
// Return the string of characters.

Examples

neutralise("--++--", "++--++") ➞ "000000"

neutralise("-+-+-+", "-+-+-+") ➞ "-+-+-+"

neutralise("-++-", "-+-+") ➞ "-+00"

Notes

The two strings will be the same length.