On day 1, one person discovers a secret. You are given an integer delay, which means that each person will share the secret with a new person every day, starting from delay days after discovering the secret. You are also given an integer forget, whi

peopleAwareOfSecret.js

/**
 * @param {number} n
 * @param {number} delay
 * @param {number} forget
 * @return {number}
 */
var peopleAwareOfSecret = function(n, delay, forget) {
    const MOD = 1e9 + 7;

    // dp[i] = number of people who learn the secret on day i
    const dp = new Array(n + 1).fill(0);
    dp[1] = 1; // Day 1: one person knows the secret

    let sharing = 0; // Total number of people who can share the secret on day i

    for (let day = 2; day <= n; day++) {
        // People who start sharing today
        if (day - delay >= 1) {
            sharing = (sharing + dp[day - delay]) % MOD;
        }

        // People who forget today (stop sharing)
        if (day - forget >= 1) {
            sharing = (sharing - dp[day - forget] + MOD) % MOD;
        }

        // People who learn the secret today
        dp[day] = sharing;
    }

    // Sum up people who still remember the secret on day n
    let total = 0;
    for (let day = n - forget + 1; day <= n; day++) {
        total = (total + dp[day]) % MOD;
    }

    return total;
};