First Timestamp When All People Are Connected

Quick Overview

First Timestamp When All People Are Connected. People are labeled0 through n-1. A log [timestamp,x,y] adds a symmetric friendship between x and y, which persists.

First Timestamp When All People Are Connected

Company: Google

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Other

### Problem People are labeled 0 through n-1. A log `[timestamp,x,y]` adds a symmetric friendship between x and y, which persists. Acquaintance includes friendship chains. Return the earliest logged timestamp when every person is connected to every other, or -1 if this never happens. ```cpp class Solution { public: int earliestAcq(vector<vector<int>>& logs, int n); }; ``` ### Examples **Example 1:** ```text Input: logs = [[8,0,1],[3,1,2]], n = 3 Output: 8 Explanation: At3 only1 and2 are connected; the event at8 connects person0. ``` **Example 2:** ```text Input: logs = [[1,0,1],[2,2,3]], n = 4 Output: -1 Explanation: The two pairs remain in separate components. ``` ### Constraints - `2 <= n <= 100`; the log list has 1 to 10000 entries. - Every log contains exactly three integers. - Timestamps lie in `[0,1000000000]` and are all distinct. - Each endpoint lies in `[0,n-1]`, with distinct endpoints in a log. - Each endpoint pair occurs at most once. ### Contract considerations Timestamps are numeric event labels, not a required calendar format. ```hint Read the boundary condition Could a later-listed log have an earlier timestamp, and how does that affect the meaning of the requested earliest time? ``` ### Boundary reminders Timestamps are numeric event labels, not a required calendar format.

Overview: First Timestamp When All People Are Connected. People are labeled0 through n-1. A log [timestamp,x,y] adds a symmetric friendship between x and y, which persists.

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Source window: 0–3 months · as of Oct 21, 2026
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Problem

People are labeled 0 through n-1. A log [timestamp,x,y] adds a symmetric friendship between x and y, which persists. Acquaintance includes friendship chains. Return the earliest logged timestamp when every person is connected to every other, or -1 if this never happens.

class Solution {
public:
    int earliestAcq(vector<vector<int>>& logs, int n);
};

Examples

Example 1:

Input: logs = [[8,0,1],[3,1,2]], n = 3
Output: 8
Explanation: At3 only1 and2 are connected; the event at8 connects person0.

Example 2:

Input: logs = [[1,0,1],[2,2,3]], n = 4
Output: -1
Explanation: The two pairs remain in separate components.

Constraints

  • 2 <= n <= 100 ; the log list has 1 to 10000 entries.
  • Every log contains exactly three integers.
  • Timestamps lie in [0,1000000000] and are all distinct.
  • Each endpoint lies in [0,n-1] , with distinct endpoints in a log.
  • Each endpoint pair occurs at most once.

Contract considerations

Timestamps are numeric event labels, not a required calendar format.

Boundary reminders

Timestamps are numeric event labels, not a required calendar format.