Get Stable Periods Count (Fungible :)

Problem Overview

• Count stable-growth periods (consecutive days) where revenue takes at most k distinct values.
• Input: array revenues of n days and integer k; Output: number of such periods modulo 1e9+7.
• Constraints: 1 ≤ n ≤ 1e5, 1 ≤ k ≤ n, revenues in [-1e9, 1e9].
• Real-world context: financial analysts tracking daily product revenue for stable growth.
• From Amazon interviews: a coding interview problem and interview question.