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 meetings[i] = [xi, yi, timei] indicates that person xi and person yi have a meeting at timei. A person m

findAllPeople.js

/**
 * @param {number} n
 * @param {number[][]} meetings
 * @param {number} firstPerson
 * @return {number[]}
 */
// Function to find all people connected to the first person
var findAllPeople = function(n, meetings, firstPerson) {
    // Initialize an array to keep track of connections
    const connected = new Array(n).fill(-1);

    // Function to find the parent of a person
    const find = (person) => connected[person] < 0 ? person : find(connected[person]);

    // Function to connect two people
    const union = (p1, p2) => {
        const pp1 = find(p1), pp2 = find(p2);

        // If they are already connected, return
        if (pp1 === pp2) return pp1;

        const r1 = connected[pp1],  r2 = connected[pp2];

        // Connect the two people
        if (r1 <= r2) {
            connected[pp1] += r2;
            connected[pp2] = pp1;
        } else {
            connected[pp2] += r1;
            connected[pp1] = pp2;
        }
    }

    // Function to reset a person's connection
    const reset = (person) => {
        const parent = find(person);
        if (parent === person) return;
        connected[parent] -= connected[person];
        connected[person] = -1;
    }

    // Connect the first person to the root (0)
    union(0, firstPerson);

    // Initialize a map to store meeting start times
    const starts = {};

    // Populate the map with meeting start times
    for (let i = 0; i < meetings.length; i++) {
        const [p1, p2, t] = meetings[i];
        starts[t] = starts[t] || [];
        starts[t].push(i);
    }

    // Get all the meeting times and sort them
    const times = Object.keys(starts).map(t => +t).sort((a, b) => a - b);

    // Initialize a set to store the result
    const res = new Set([0, firstPerson]);

    // For each meeting time
    for(const time of times) {
        const set = new Set();
        // For each meeting starting at this time
        for(const i of starts[time]) {
            const [p1, p2, t] = meetings[i];
            // Connect the two people in the meeting
            union(p1, p2);
            // Add them to the set
            set.add(p1);
            set.add(p2);
        }
        // For each person in the set
        for(const p of set) {
            // If the person is not connected to the root, reset their connection
            if(find(p) !== find(0)) {
                reset(p);
            } else {
                // Otherwise, add them to the result
                res.add(p);
            }
        }
    }

    // Return the result as an array
    return [...res];
};