Problem

Given a list of numbers, write a Python program to find the sum of the even-numbered elements in the list.
Example input: [1, 2, 3, 4, 5]
Example output: 6

Solution

# Solution:

def sum_even(numbers):
    sum = 0
    for number in numbers:
        if number % 2 == 0:
            sum += number
    return sum

# Explanation:

# The solution above is optimal because it only iterates through the list once.
# It also uses the modulo operator to check if the number is even.
# The modulo operator is a fast way to check if a number is even.
# If the number is even, the modulo operator will return 0.
# If the number is odd, the modulo operator will return 1.
# The modulo operator is faster than using the division operator.
# The division operator will return a float, which is slower than an integer.
# The modulo operator will return an integer.