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Solution: Number of People Aware of a Secret

Explore how to apply dynamic programming concepts to solve the problem of tracking how many people know a secret after n days, considering delay and forget periods. Understand the use of a dp array to represent new learners each day and efficiently update sharing counts to handle constraints. This lesson teaches you how to implement this approach in C++ with modular arithmetic for large results.

Statement

On day 11, exactly one person discovers a secret.

Each person who learns the secret will begin sharing it with one new person every day, but only after a waiting period of delay days from when they first discovered it. Additionally, each person completely forgets the secret forget days after discovering it. Once a person has forgotten the secret (on the day of forgetting and all subsequent days), they can no longer share it.

Given an integer n, determine how many people know the secret at the end of day n. Since the result can be very large, return it modulo 109+710^9 + 7.

Note: A person who discovered the secret on day d can share it starting from day d + delay through day d + forget - 1 (inclusive), and they forget it on day d + forget.

Constraints:

  • 22 \leq ...