Suppose we have an array of objects like this −const arr = [    {_id : "1", S : "2"},    {_id : "1", M : "4"},    {_id : "2", M : "1"},    {_id : "" , M : "1"},    {_id : "3", S : "3"} ];We are required to write a JavaScript function that takes in one such array and groups all the objects together that have the same value for the '_id' key.Therefore, the final output should look something like this −const output = [    {_id : "1", M : "4", S : "2", ... Read More

Given an array of five positive integers, we are required to find the minimum and maximum values that can be calculated by summing exactly four of the five integers.Then print the respective minimum and maximum values as a single line of two spaceseparated long integers.The array is not sorted all the times.For example −const arr = [1, 3, 5, 7, 9]The minimum sum is −1 + 3 + 5 + 7 = 16and the maximum sum is −3 + 5 + 7 = 24The return value of the function should be −[16, 24];ExampleThe code for this will be −const arr ... Read More

Suppose, we have a long string that represents a number like this −const str = '11222233344444445666';We are required to write a JavaScript function that takes in one such string. Our function is supposed to return an object that should assign a unique "id" property to each unique number in the string and one other property "count" that stores the count of the number of times the number appears in the string.Therefore, for the above string, the output should look like −const output = {    '1': { id: '1', displayed: 2 },    '2': { id: '2', displayed: 4 }, ... Read More

We are required to write a JavaScript function that takes in an array of sorted integers and a target average as first and second arguments.The function should determine whether there is a pair of values in the array where the average of the pair equals to the target average.There's a solution with O(1) additional space complexity and O(n) time complexity. Since an array is sorted, it makes sense to have two indices: one going from begin to end (say y), another from end to begin of an array (say x).ExampleThe code for this will be −const arr = [1, 2, ... Read More

Suppose, we have an array of arrays like this −const arr = [[12345, "product", "10"], [12345, "product", "15"], [1234567, "other", "10"]];We are supposed to write a function that takes in one such array. Notice that all the subarrays have precisely three elements in them.Our function should filter out that subarray which has a repeating value as its first element. Moreover, for the subarray, we remove we should add their third element to its existing nonrepeating counterpart.So, for the above array, the output should look like −const output = [[12345, "product", "25"], [1234567, "other", "10"]];ExampleThe code for this will be −const ... Read More

In JavaScript, there are scenarios where you may need to generate every possible combination of a string's characters. This can be especially useful in areas like cryptography, analyzing subsets of data, or solving problems involving permutations. In this article, we’ll learn to implement a JavaScript function to achieve this task. Generate all combinations of supplied words Following are the different approaches for generating all combinations of supplied words − Recursive Approach Iterative Approach Using Bitmasking Using Recursive Approach The function iterates over each character in the string, appending ... Read More

Consider the following backtracing problem: On a 2−dimensional grid, there are 4 types of squares −1 represents the starting square. There is exactly one starting square.2 represents the ending square. There is exactly one ending square.0 represents empty squares we can walk over.−1 represents obstacles that we cannot walk over.We are required to write a function that returns the number of 4−directional walks from the starting square to the ending square, that walk over every non−obstacle square exactly once.Exampleconst arr = [    [1, 0, 0, 0],    [0, 0, 0, 0],    [0, 0, 2, -1] ]; const uniquePaths ... Read More

We are required to write a function that does the following −takes an array of integers as an argument (e.g. [1, 2, 3, 4])creates an array of all the possible permutations of [1, 2, 3, 4], with each permutation having a length of 4 (i.e., the length of original array)ExampleThe code for this will be −const arr = [1, 2, 3, 4]; const permute = (arr = [], res = [], used = []) => {    let i, ch;    for (i = 0; i < arr.length; i++) {       ch = arr.splice(i, 1)[0];       ... Read More

Suppose, we have an array of objects containing data about likes of some users like this −const arr = [    {"user":"dan", "liked":"yes", "age":"22"},    {"user":"sarah", "liked":"no", "age":"21"},    {"user":"john", "liked":"yes", "age":"23"},  ];We are required to write a JavaScript function that takes in one such array. The function should construct another array based on this array like this −const output = [    {"dan":"yes"},    {"sarah":"no"},    {"john":"yes"}, ];Exampleconst arr = [    {"user":"dan", "liked":"yes", "age":"22"},    {"user":"sarah", "liked":"no", "age":"21"},     {"user":"john", "liked":"yes", "age":"23"}, ]; const mapToPair = (arr = []) => {    const result = arr.map(obj => ... Read More

We are required to write a JavaScript function that takes in an array of Numbers as the first argument and a target sum Number as the second argument.The function should return an array of all those subarrays from the original array whose elements sum to make the target sum. We can use a single number twice to achieve the sum.For example −If the input array and number are −const arr = [1, 2, 4]; const sum = 4;then the output should be −const output = [    [1, 1, 1, 1],    [1, 1, 2],    [2, 2],    [4] ... Read More