Happy Numbers

You are given a list of 0s and 1s, like the one below:

[0, 1, 0, 0, 0, 1, 1, 1, 0, 1]

# The first element, a 0, and the last element, a 1 are both unhappy.
# The second element, a 1 is unhappy.
# The second-to-last element, a 0 is unhappy.
# All other numbers in this list are happy.

A 1 is unhappy if the digit to its left and the digit to its right are both 0s. A 0 is unhappy if the digit to its left and the digit to its right are both 1s. If a number has only one neighbor, it is unhappy if its only neighbor is different. Otherwise, a number is happy.

Write a function that takes in a list of 0s and 1s and outputs the portion of numbers which are happy. The total portion of numbers which are happy can be represented as:

portion of happy numbers = (happy 0s + happy 1s) / total numbers

In the example above, 0.6 is the number of happy numbers.

Examples

portion_happy([0, 1, 0, 1, 0]) ➞ 0

portion_happy([0, 1, 1, 0]) ➞ 0.5

portion_happy([0, 0, 0, 1, 1]) ➞ 1

portion_happy([1, 0, 0, 1, 1]) ➞ 0.8

Notes

• Remember: a 0 border number is unhappy if its only neighbor is a 1 and vice versa.
• A list will contain at least two elements.