Question
Given a list of integers, find the leftmost balance index: a position where the sum of all entries strictly to its left equals the sum of all entries strictly to its right (the entry at the position itself joins neither side). Sums over no entries count as 0. Return that index, or -1 if no position balances. Example: [1, 7, 3, 6, 5, 6] returns 3, since 1+7+3 = 5+6.
balance_index(nums: list[int]) → int[[1,7,3,6,5,6]]out3State 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.
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.