Sensors

Solution to SafetyCulture's coding challenge

Problem description

We are collecting temperature data about fridges in a supermarket. Imagine we have data from.different fridge sensors aggregated into a single JSON array (where an individual sensor is identified by an id):

Input

[{"id": "a","timestamp": 1509493641,"temperature": 3.53},
{"id": "b","timestamp": 1509493642,"temperature": 4.13},
{"id": "c","timestamp": 1509493643,"temperature": 3.96},
{"id": "a","timestamp": 1509493644,"temperature": 3.63},
{"id": "c","timestamp": 1509493645,"temperature": 3.96},
{"id": "a","timestamp": 1509493645,"temperature": 4.63},
{"id": "a","timestamp": 1509493646,"temperature": 3.53},
{"id": "b","timestamp": 1509493647,"temperature": 4.15},
{"id": "c","timestamp": 1509493655,"temperature": 3.95},
{"id": "a","timestamp": 1509493677,"temperature": 3.66},
{"id": "b","timestamp": 1510113646,"temperature": 4.15},
{"id": "c","timestamp": 1510127886,"temperature": 3.36},
{"id": "c","timestamp": 1510127892,"temperature": 3.36},
{"id": "a","timestamp": 1510128112,"temperature": 3.67},
{"id": "b","timestamp": 1510128115,"temperature": 3.88}]

Output

[
 {
  "id": "b",
  "average": 4.08,
  "median": 4.15,
  "mode": [
   4.15
  ]
 },
 {
  "id": "c",
  "average": 3.72,
  "median": 3.95,
  "mode": [
   3.36,
   3.96
  ]
 },
 {
  "id": "a",
  "average": 3.78,
  "median": 3.66,
  "mode": [
   3.53
  ]
 }
]

How to run

From a terminal run with optional parameters. If no parameters are given then the program assumes the file input.json to be present in the same directory.

go run ./cmd/cli.sensor.data/main.go -input input.json -output output.json

Tests

go test

Build

Building this file will generate a cli.sensor.data binary file

go build ./cmd/cli.sensor.data/

Vendoring

Used dep for dependencies

Assumptions

1. I decided to use float64 to represent the temperature. The result may vary depending on where the program runs due to actual representation of floating point numbers. For a more accurate representation I would have used the decimal package

2. I did not implement my own Sort nor Round functions

3. Reading a file into memory could be dangerous if it's too big and can cause a memory issue depending on the instance where it runs

4. The mode function is not the most optimal implementation as various iterations over different arrays isn't the best approach. There is probably a better or more complicated mathematical solution to obtain that value