First and Last Occurrence of Element in DSA Typescript - Build from Scratch

First and Last Occurrence of Element

📖 Scenario: You are working with a list of product IDs sold in a store during a day. Some products appear multiple times because they were sold multiple times.You want to find the first and last time a specific product was sold to understand its sales pattern.

🎯 Goal: Build a program that finds the first and last position of a given product ID in the sales list.

📋 What You'll Learn

Create an array called sales with the exact product IDs: [101, 203, 101, 405, 203, 101, 507]

Create a variable called targetProduct and set it to 101

Write a loop to find the first and last index of targetProduct in sales

Print the first and last occurrence indexes in the format: First occurrence: X, Last occurrence: Y

💡 Why This Matters

🌍 Real World

Stores and businesses often analyze sales data to understand when products are sold during the day. Finding first and last occurrences helps in tracking product demand and stock management.

💼 Career

This skill is useful for data analysts, software developers, and anyone working with data searching and processing in real-world applications.

1

Create the sales data array

Create an array called sales with these exact product IDs: [101, 203, 101, 405, 203, 101, 507]

DSA Typescript

// Create the sales array with the given product IDs
// Your code here

Hint

Use const sales = [101, 203, 101, 405, 203, 101, 507]; to create the array.

2

Set the target product ID

Create a variable called targetProduct and set it to 101

DSA Typescript

const sales = [101, 203, 101, 405, 203, 101, 507];
// Create targetProduct variable and set it to 101
// Your code here

Hint

Use const targetProduct = 101; to set the product ID.

3

Find first and last occurrence indexes

Write a for loop with variable i from 0 to sales.length - 1 to find the first and last index of targetProduct in sales. Use variables firstIndex and lastIndex initialized to -1 before the loop. Update firstIndex when you find the first match, and update lastIndex every time you find a match.

DSA Typescript

const sales = [101, 203, 101, 405, 203, 101, 507];
const targetProduct = 101;
let firstIndex = -1;
let lastIndex = -1;
// Write a for loop to find first and last occurrence of targetProduct
// Your code here

Hint

Use a for loop and check each element. Set firstIndex only once when you find the first match. Update lastIndex every time you find a match.

4

Print the first and last occurrence

Print the first and last occurrence indexes using console.log in this exact format: First occurrence: X, Last occurrence: Y where X is firstIndex and Y is lastIndex

DSA Typescript

const sales = [101, 203, 101, 405, 203, 101, 507];
const targetProduct = 101;
let firstIndex = -1;
let lastIndex = -1;
for (let i = 0; i < sales.length; i++) {
    if (sales[i] === targetProduct) {
        if (firstIndex === -1) {
            firstIndex = i;
        }
        lastIndex = i;
    }
}
// Print the first and last occurrence indexes
// Your code here

Hint

Use console.log(`First occurrence: ${firstIndex}, Last occurrence: ${lastIndex}`); to print the result.