Binary Search Recursive Approach in DSA Javascript - Build from Scratch

Binary Search Recursive Approach

📖 Scenario: You have a sorted list of numbers representing book IDs in a library. You want to find if a specific book ID is available using a fast method.

🎯 Goal: Build a recursive binary search function in JavaScript that checks if a given book ID exists in the sorted list.

📋 What You'll Learn

Create a sorted array called bookIDs with the exact values: [101, 203, 305, 407, 509, 611, 713]

Create a variable called targetID and set it to 407

Write a recursive function called binarySearch that takes arr, target, start, and end as parameters

Use recursion to find if targetID is in bookIDs

Print true if found, otherwise false

💡 Why This Matters

🌍 Real World

Binary search is used in many applications like searching in databases, looking up words in dictionaries, or finding items in sorted lists quickly.

💼 Career

Understanding binary search helps in software development roles that require efficient data searching and algorithm optimization.

1

Create the sorted array of book IDs

Create a sorted array called bookIDs with these exact values: [101, 203, 305, 407, 509, 611, 713]

DSA Javascript

// Create the sorted array bookIDs with the given values
// Your code here

Hint

Use const bookIDs = [101, 203, 305, 407, 509, 611, 713]; to create the array.

2

Set the target book ID to search

Create a variable called targetID and set it to 407

DSA Javascript

const bookIDs = [101, 203, 305, 407, 509, 611, 713];
// Create the variable targetID and set it to 407
// Your code here

Hint

Use const targetID = 407; to store the book ID you want to find.

3

Write the recursive binary search function

Write a recursive function called binarySearch that takes parameters arr, target, start, and end. It should return true if target is found in arr, otherwise false. Use recursion to check the middle element and search the left or right half accordingly.

DSA Javascript

const bookIDs = [101, 203, 305, 407, 509, 611, 713];
const targetID = 407;

// Write the recursive binarySearch function below
// Your code here

Hint

Use the middle index to compare and call binarySearch recursively on the left or right half.

4

Print the result of searching for the target ID

Use console.log to print the result of calling binarySearch with bookIDs, targetID, 0 as start, and bookIDs.length - 1 as end.

DSA Javascript

const bookIDs = [101, 203, 305, 407, 509, 611, 713];
const targetID = 407;

function binarySearch(arr, target, start, end) {
    if (start > end) {
        return false;
    }
    const mid = Math.floor((start + end) / 2);
    if (arr[mid] === target) {
        return true;
    } else if (arr[mid] > target) {
        return binarySearch(arr, target, start, mid - 1);
    } else {
        return binarySearch(arr, target, mid + 1, end);
    }
}

// Print the result of binarySearch with bookIDs, targetID, 0, and bookIDs.length - 1
// Your code here

Hint

Call binarySearch(bookIDs, targetID, 0, bookIDs.length - 1) and print the result.