Searching in JavaScript

Linear Search in JavaScript

const arr = [1, 2, 6, 9, 0, -5];

const linearSearch = (arr, target) => {
    for (let i = 0; i < arr.length; i++) {
        if (arr[i] === target) {
            return i;
        }
    }
    return -1;
}

console.log(linearSearch(arr, 8));
console.log(arr.includes(9));
console.log(arr.indexOf(9));
console.log(arr.find((num) => num > 0));
console.log(arr.findIndex((num) => num < 0));

Binary Search In JavaScript

const BinarySearch = (arr, target) => {
    let start = 0, end = arr.length - 1;
    while (start <= end) {
        let mid = Math.floor((start + end) / 2);

        if (arr[mid] === target) {
            return mid;
        }

        else if (arr[mid] > target) {
            end = mid - 1;
        }

        else {
            start = mid + 1;
        }
    }

    return -1;
}

console.log(BinarySearch([1, 4, 6, 9, 12, 15], 8));

Binary Search using Recursion

const BinarySearchRecur = (arr, target) => {
    return BinarySearchUtil(arr, target, 0, arr.length);
}

const BinarySearchUtil = (arr, target, start, end) => {
    if (start > end)
        return -1;

    let mid = Math.floor((start + end) / 2);

    if (arr[mid] === target) {
        return mid;
    }

    else if (arr[mid] > target) {
        return BinarySearchUtil(arr, target, start, mid - 1);
    }

    else {
        return BinarySearchUtil(arr, target, mid + 1, end);
    }
}

Find floor and ceil value of X in an array

const floorCeil = (arr, target) => {
    let start = 0, end = arr.length;
    let floor = -1, ceil = -1;
    while(start <= end){
        let mid = Math.floor((start + end)/2);

        if(arr[mid] === target){
            floor = mid;
            ceil = mid;
            return [ceil, mid]
        }

        else if(arr[mid] > target){
            ceil = mid;
            end = mid - 1;
        }

        else {
            floor = mid;
            start = mid + 1;
        }
    }

    return [ceil, floor]
}

Practice Questions

Level 1

• Sqrt(x)
• First Bad Version
• Find the Index of the First Occurrence in a String
• Binary Search
• Search Insert Position
• Find Minimum in Rotated Sorted Array

Level 2

• Find First and Last Position of Element in Sorted Array
• Single Element in a Sorted Array
• Search a 2D Matrix
• Find Peak Element
• Search in Rotated Sorted Array