JavaScript problem solving

This project contains solutions for two common programming problems in JavaScript:

1. finding missing numbers in a range
2. finding two numbers that sum to a specific target.

Installation

To install the necessary dependencies, execute:

npm install

Testing

This project uses Jest to perform unit tests. To run the tests, use the following command:

npm test

Problems

1. missingNumbers: Given a list of integers where each integer is in the range from 1 to the length of the list, this function returns a list of all the integers in that range that do not appear in the list.

• Code: src/missingNumbers.js
• Tests: tests/missingNumbers.test.js
• Time complexity: O(n^2) due to the use of the includes function within a loop.
• Space completixy: O(n) where n is the length of the input list.

// missingNumbers.js
function missingNumbers(nums) {
  let result = [];
  
  for(let i = 1; i <= nums.length; i++) {
    if(!nums.includes(i)) {
      result.push(i);
    }
  }
  return result;
}

// missingNumbers.test.js
const missingNumbers = require('../src/missingNumbers');

test('missingNumbers function exists', () => {
  expect(missingNumbers).toBeDefined();
});

test('find missing numbers in the array', () => {
  expect(missingNumbers([4,3,2,7,8,2,3,1])).toEqual([5,6]);
  expect(missingNumbers([1,1])).toEqual([2]);
});

2. twoSum: Given a list of integers and an integer target, this function returns the indices of two numbers that sum to that target. It assumes that there is exactly one solution and that the same element cannot be used twice.

• Code: src/twoSum.js
• Tests: tests/missingNumbers.test.js
• Time completixy: O(n) where n is the length of the input list. This is because we iterate through the list once.
• Space complexity: O(n) where n is the length of the input list. We store each number and its index in an object as we iterate through the list.

// twoSum.js
function twoSum(nums, target) {
  let map = {};
  for(let i = 0; i < nums.length; i++) {
    let complement = target - nums[i];
    if(map[complement] !== undefined) {
      return [map[complement], i];
    }
    map[nums[i]] = i;
  }
}

// twoSum.test.js
const twoSum = require('../src/twoSum');

test('twoSum function exists', () => {
  expect(twoSum).toBeDefined();
});

test('find two indices that their values sum up to the target', () => {
  expect(twoSum([2,7,11,15], 9)).toEqual([0,1]);
  expect(twoSum([3,2,4], 6)).toEqual([1,2]);
  expect(twoSum([3,3], 6)).toEqual([0,1]);
});