CodingEasycod-g1186

Subject ArraysLevel Entry–Mid~12 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Given a list of integers, count the unordered pairs of positions (i, j) with i < j whose values sum to an even number. Two values sum to an even number exactly when they have the same parity. Aim for a solution that does not compare every pair directly. Example: [1, 2, 3, 4] has 2 such pairs: (1, 3) and (2, 4).

Implement

even_sum_pairs(nums: list[int]) → int

Examples

in[[1,2,3,4]]out2

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.