Longest Consecutive-Day Streak

Problem

Given `logins(user_id, login_date)` (one row per user/day), return each user's longest streak of consecutive days logged in. Output (user_id, longest_streak).

Input

logins

Output

user_id, longest_streak

Constraints

1 ≤ rows ≤ 10^6

Sample input

user 1: Jan 1,2,3,5,6 → streak 3

Sample output

1,3

Explanation

Classic 'island' problem: subtract a row-number from the date — consecutive dates collapse to a constant.

window-fnrow-numbergaps-and-islands@Netflix

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