Minimum Number of Platforms in DSA Typescript - Build from Scratch

Minimum Number of Platforms

📖 Scenario: You are managing a small train station. You want to find out the minimum number of platforms needed so that no train has to wait.Each train has an arrival time and a departure time.

🎯 Goal: Build a program that calculates the minimum number of platforms required for the trains given their arrival and departure times.

📋 What You'll Learn

Create two arrays called arrivals and departures with exact train times.

Create a variable called n to store the number of trains.

Write logic to find the minimum number of platforms needed using the arrival and departure arrays.

Print the minimum number of platforms required.

💡 Why This Matters

🌍 Real World

Train stations and airports use this logic to manage platforms or gates so that vehicles do not wait and operations run smoothly.

💼 Career

This problem teaches how to handle overlapping intervals and resource allocation, which is useful in scheduling, event planning, and system design roles.

1

Create train arrival and departure arrays

Create an array called arrivals with these exact values: 900, 940, 950, 1100, 1500, 1800. Also create an array called departures with these exact values: 910, 1200, 1120, 1130, 1900, 2000.

DSA Typescript

// Create the arrivals and departures arrays with exact values
// Your code here

Hint

Use const arrivals = [...] and const departures = [...] with the exact numbers given.

2

Create variable for number of trains

Create a variable called n and set it to the length of the arrivals array.

DSA Typescript

const arrivals = [900, 940, 950, 1100, 1500, 1800];
const departures = [910, 1200, 1120, 1130, 1900, 2000];
// Create variable n for number of trains
// Your code here

Hint

Use const n = arrivals.length; to get the number of trains.

3

Calculate minimum number of platforms needed

Write code to calculate the minimum number of platforms needed. Sort the arrivals and departures arrays. Use two pointers i and j starting at 0. Use variables platforms_needed and max_platforms initialized to 0. Loop while i < n and j < n. If arrivals[i] <= departures[j], increment platforms_needed and i. Else decrement platforms_needed and increment j. Update max_platforms with the maximum of itself and platforms_needed inside the loop.

DSA Typescript

const arrivals = [900, 940, 950, 1100, 1500, 1800];
const departures = [910, 1200, 1120, 1130, 1900, 2000];
const n = arrivals.length;
// Calculate minimum platforms needed
// Your code here

Hint

Sort both arrays. Use two pointers and count platforms needed. Update max platforms inside the loop.

4

Print the minimum number of platforms

Print the value of max_platforms.

DSA Typescript

const arrivals = [900, 940, 950, 1100, 1500, 1800];
const departures = [910, 1200, 1120, 1130, 1900, 2000];
const n = arrivals.length;

arrivals.sort((a, b) => a - b);
departures.sort((a, b) => a - b);

let platforms_needed = 0;
let max_platforms = 0;

let i = 0;
let j = 0;

while (i  max_platforms) {
      max_platforms = platforms_needed;
    }
  } else {
    platforms_needed--;
    j++;
  }
}
// Print the minimum number of platforms
// Your code here

Hint

Use console.log(max_platforms); to print the result.