Level 3Exercise #74

First negative per window

For each window of k numbers, return its first negative number or 0 in O(n).

What you’ll practice

This Level 3 exercise focuses on monotonic deque in the Collections curriculum. Solve the challenge prompt above using clear, idiomatic Python and the relevant language or standard-library tools.

Relevant Python reference: collections.deque.

Sample Test Cases

Example #1

Input:first_negatives([2,-1,3,-4,5], k=3)

Output:[-1,-1,-4]

Reference Solution

Reveal Reference Solution

def first_negatives(values: list[int], k: int) -> list[int]:
    from collections import deque
    negatives, result = deque(), []
    for i, value in enumerate(values):
        if value < 0: negatives.append(i)
        while negatives and negatives[0] <= i-k: negatives.popleft()
        if i >= k-1: result.append(values[negatives[0]] if negatives else 0)
    return result

Pro Tips & Keyboard Shortcuts

Color Theme

Ctrl + K then T

Open VS Code Color Theme Quick Pick to select from 20 dark and light themes.

Editor SettingsCtrl + K

Open practice settings drawer to toggle line numbers, indenting, font size & hints.

Search MenuCtrl + /

Expand sidebar menu, focus search bar, and highlight search text instantly.

Focus Code Editor

Esc or Ctrl + `

Instantly highlight and focus code editor from anywhere, restoring cursor right where you left off.

Normal ViewEsc

Collapse sidebar and close all popups or settings drawers for clean focus view.

First negative per window

What you’ll practice

Sample Test Cases

Further Reading

Reference Solution