Question
A fitness challenge unlocks a badge the first time a member logs at least target total steps across k consecutive days. Given the daily list steps and the window length k (1 <= k <= number of days), return the 0-based start index of the FIRST window of k days whose sum reaches target, or -1 if it never happens. Slide a running sum and return as soon as the condition is met. Example: steps = [2000, 3000, 5000, 6000], k = 2, target = 9000 gives 2.
first_badge_window(steps: list[int], k: int, target: int) → int[[2000,3000,5000,6000],2,9000]out2State 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.