Real interview questions from top companies for Array. Includes theoretical concepts and coding problems.
What is an array in programming?
An array is a collection of elements of the same data type stored in contiguous memory locations.
What are the advantages of using arrays?
Arrays allow for efficient storage and retrieval of data, and they can be used to implement various data structures such as stacks and queues.
How do you initialize an array in JavaScript?
In JavaScript, an array can be initialized using the array literal syntax, for example: let arr = [1, 2, 3, 4, 5];
What is the difference between a one-dimensional and a multi-dimensional array?
A one-dimensional array is a collection of elements of the same data type stored in contiguous memory locations, while a multi-dimensional array is an array of arrays, where each element is itself an array.
How do you access an element in an array?
An element in an array can be accessed using its index, which is a numerical value that represents the position of the element in the array.
What is the purpose of the length property in an array?
The length property in an array returns the number of elements in the array.
How do you iterate over an array in JavaScript?
In JavaScript, an array can be iterated over using a for loop, a for...of loop, or the forEach method.
What is the difference between the push and unshift methods in an array?
The push method adds one or more elements to the end of an array, while the unshift method adds one or more elements to the beginning of an array.
How do you remove an element from an array in JavaScript?
In JavaScript, an element can be removed from an array using the splice method or the pop method.
What is the purpose of the splice method in an array?
The splice method in an array is used to add or remove elements from a specific position in the array.
How do you sort an array in JavaScript?
In JavaScript, an array can be sorted using the sort method, which sorts the elements of the array in place and returns the sorted array.
What is the difference between the sort and reverse methods in an array?
The sort method sorts the elements of an array in ascending or descending order, while the reverse method reverses the order of the elements in the array.
How do you find the maximum or minimum value in an array?
The maximum or minimum value in an array can be found using the Math.max or Math.min function in combination with the spread operator or the apply method.
What is the purpose of the every and some methods in an array?
The every method tests whether all elements in an array pass a test implemented by a provided function, while the some method tests whether at least one element in an array passes a test implemented by a provided function.
Write a JavaScript function to find the first duplicate in an array of integers.
functionfindFirstDuplicate(arr) {
let seen = newSet();
for (let i = 0; i < arr.length; i++) {
if (seen.has(arr[i])) {
return arr[i];
}
seen.add(arr[i]);
}
returnnull;
}
Write a JavaScript function to find the maximum sum of a subarray within a given array of integers.
functionmaxSubarraySum(arr) {
let maxSum = -Infinity;
for (let i = 0; i < arr.length; i++) {
let currentSum = 0;
for (let j = i; j < arr.length; j++) {
currentSum += arr[j];
maxSum = Math.max(maxSum, currentSum);
}
}
return maxSum;
}
Write a JavaScript function to find the missing number in an array of consecutive integers.
functionfindMissingNumber(arr) {
let n = arr.length + 1;
let expectedSum = (n * (n + 1)) / 2;
let actualSum = arr.reduce((a, b) => a + b, 0);
return expectedSum - actualSum;
}
Write a JavaScript function to find the pair of elements in an array that add up to a given target sum.
functionfindPairWithSum(arr, targetSum) {
let seen = newSet();
for (let i = 0; i < arr.length; i++) {
let complement = targetSum - arr[i];
if (seen.has(complement)) {
return [complement, arr[i]];
}
seen.add(arr[i]);
}
returnnull;
}
Write a JavaScript function to find the longest increasing subsequence in an array of integers.
functionlongestIncreasingSubsequence(arr) {
let lengths = newArray(arr.length).fill(1);
for (let i = 1; i < arr.length; i++) {
for (let j = 0; j < i; j++) {
if (arr[i] > arr[j] && lengths[i] < lengths[j] + 1) {
lengths[i] = lengths[j] + 1;
}
}
}
returnMath.max(...lengths);
}
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