Count Evens

Unit 1 Session A

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Are all elements in the list positive integers?
  • Yes.
• Can the list be empty?
  • Yes. In that case, your function should return zero.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Create a function that counts how many even numbers are in a list of integers.

1) Create a count variable with an initial count of zero
2) For each element in the list
  a) Check if the number is even
  b) If so, increment the count by 1
3) Return the count

⚠️ Common Mistakes

• A number is even when it is evenly divisible by two. How can we check that in python?

I-mplement

def count_evens(lst):
	count = 0
	for num in lst:
		if num % 2 == 0:
			count += 1
	return count