2092 - Find All People With Secret.

Hard

You are given an integer n indicating there are n people numbered from 0 to n - 1. You are also given a 0-indexed 2D integer array meetings where <code>meetingsi = x_i, y_i, time_i</code> indicates that person <code>x_i</code> and person <code>y_i</code> have a meeting at <code>time_i</code>. A person may attend multiple meetings at the same time. Finally, you are given an integer firstPerson.

Person 0 has a secret and initially shares the secret with a person firstPerson at time 0. This secret is then shared every time a meeting takes place with a person that has the secret. More formally, for every meeting, if a person <code>x_i</code> has the secret at <code>time_i</code>, then they will share the secret with person <code>y_i</code>, and vice versa.

The secrets are shared instantaneously. That is, a person may receive the secret and share it with people in other meetings within the same time frame.

Return a list of all the people that have the secret after all the meetings have taken place. You may return the answer in any order.

Example 1:

Input: n = 6, meetings = \[\[1,2,5],2,3,8,1,5,10], firstPerson = 1

Output: 0,1,2,3,5

Explanation:

At time 0, person 0 shares the secret with person 1.

At time 5, person 1 shares the secret with person 2.

At time 8, person 2 shares the secret with person 3.

At time 10, person 1 shares the secret with person 5.

Thus, people 0, 1, 2, 3, and 5 know the secret after all the meetings.

Example 2:

Input: n = 4, meetings = \[\[3,1,3],1,2,2,0,3,3], firstPerson = 3

Output: 0,1,3

Explanation:

At time 0, person 0 shares the secret with person 3.

At time 2, neither person 1 nor person 2 know the secret.

At time 3, person 3 shares the secret with person 0 and person 1.

Thus, people 0, 1, and 3 know the secret after all the meetings.

Example 3:

Input: n = 5, meetings = \[\[3,4,2],1,2,1,2,3,1], firstPerson = 1

Output: 0,1,2,3,4

Explanation:

At time 0, person 0 shares the secret with person 1.

At time 1, person 1 shares the secret with person 2, and person 2 shares the secret with person 3.

Note that person 2 can share the secret at the same time as receiving it.

At time 2, person 3 shares the secret with person 4.

Thus, people 0, 1, 2, 3, and 4 know the secret after all the meetings.

Constraints:

• <code>2 <= n <= 10⁵</code>

• <code>1 <= meetings.length <= 10⁵</code>

• meetings[i].length == 3

• <code>0 <= x_i, y_i<= n - 1</code>

• <code>x_i != y_i</code>

• <code>1 <= time_i<= 10⁵</code>

• 1 <= firstPerson <= n - 1