RoofTop Food Delivery System

A Spring Boot REST API that assigns delivery drivers to customer orders based on availability and timing.

Problem

Assign M drivers to N customer orders where:

• Each order has: order time (O) and travel time (T)
• Drivers are assigned by lowest index first (D1, then D2, etc.)
• Drivers can only handle one order at a time
• If all drivers are busy, return "No Food :-("

Tech Stack

• Java 17
• Spring Boot 2.7.14
• Spring Data JPA
• H2 Database (in-memory)
• Maven

Quick Start

1. Build

mvn clean install

2. Run

mvn spring-boot:run

3. Test

curl http://localhost:8080/api/delivery/health

curl -X POST http://localhost:8080/api/delivery/process \
  -H "Content-Type: application/json" \
  -d '{
    "numberOfCustomers": 6,
    "numberOfDrivers": 2,
    "orders": [
      {"orderTime": 1, "travelTime": 10},
      {"orderTime": 4, "travelTime": 20},
      {"orderTime": 15, "travelTime": 5},
      {"orderTime": 22, "travelTime": 20},
      {"orderTime": 24, "travelTime": 10},
      {"orderTime": 25, "travelTime": 10}
    ]
  }'

Expected: C1-D1, C2-D2, C3-D1, C4-D1, C5-D2, C6-No Food :-(

API Endpoints

Base URL: http://localhost:8080/api/delivery

Method	Endpoint	Description
POST	/process	Process orders and assign drivers
GET	/drivers	Get all drivers
GET	/customers	Get all customers
GET	/assignments	Get assignment history
POST	/reset	Clear all data
GET	/health	Health check

How It Works

The assignment logic uses a PriorityQueue to efficiently find available drivers:

1. Initialize drivers with availableAt = 0
2. Load drivers into a min-heap (sorted by availability time, then driver index)
3. For each order:
   • Check the driver at the top of the heap
   • If availableAt <= orderTime: assign them, update their time, re-insert
   • Otherwise: "No Food :-("

Why PriorityQueue? Instead of checking all M drivers for each order (O(N×M)), the heap gives us the next available driver in O(log M) time. For scale (think 1000 orders, 100 drivers), this cuts ~100K operations down to ~6.6K.

Complexity: O(N log M) time, O(M) space

Example

Given 6 customers and 2 drivers:

Customer	Order Time	Travel Time	D1 Free At	D2 Free At	Assigned
C1	1	10	0	0	D1
C2	4	20	11	0	D2
C3	15	5	11	24	D1
C4	22	20	20	24	D1
C5	24	10	42	24	D2
C6	25	10	42	34	No Food

Project Structure

food-delivery-system/
├── src/
│   └── main/
│       ├── java/com/rooftop/delivery/
│       │   ├── FoodDeliveryApplication.java
│       │   ├── controller/
│       │   │   └── DeliveryController.java
│       │   ├── service/
│       │   │   └── DeliveryAssignmentService.java
│       │   ├── repository/
│       │   │   ├── DriverRepository.java
│       │   │   ├── CustomerRepository.java
│       │   │   └── DeliveryAssignmentRepository.java
│       │   ├── model/
│       │   │   ├── Driver.java
│       │   │   ├── Customer.java
│       │   │   └── DeliveryAssignment.java
│       │   └── dto/
│       │       ├── OrderRequest.java
│       │       ├── BatchOrderRequest.java
│       │       └── AssignmentResponse.java
│       └── resources/
│           └── application.properties
├── screenshots/
│   ├── healthapi.png
│   ├── apideliveryprocesspost.png
│   ├── apideliverydriversget.png
│   ├── apideliverycustomersget.png
│   ├── apideliveryassignmentsget.png
│   └── apideliveryresetpost.png
├── pom.xml
├── input.txt
├── schema-mysql.sql
├── .gitignore
├── README.md
└── DOCUMENTATION.md

Database

Uses H2 in-memory database by default. Access H2 console at:

• URL: http://localhost:8080/h2-console
• JDBC URL: jdbc:h2:mem:rooftop_delivery
• Username: sa
• Password: (empty)

Tables

drivers: Tracks driver ID, status, and availability time
customers: Stores customer orders and assignments
delivery_assignments: Complete audit trail of assignments

Optional: MySQL Setup

1. Install MySQL 8.0+
2. Create database: CREATE DATABASE rooftop_delivery;
3. Update application.properties:
   • Comment out H2 config
   • Uncomment MySQL config
   • Set your password

Screenshots

API Endpoints

Input File Format

You can also use input.txt:

6,2          # N customers, M drivers
1,10         # orderTime, travelTime
4,20
15,5
22,20
24,10
25,10

Testing Tools

cURL: See examples above
Postman: Import endpoints, set base URL to http://localhost:8080
H2 Console: Run SQL queries directly

For detailed technical documentation, see DOCUMENTATION.md