Added the new algorithm TwoSum using array in Data Structure #1854

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	/**
	* This function will accept an array and a target value,
	* and return the indexes of the two numbers that add up to the target.
	* If no such pair exists, it returns null.
	* @param {number[]} nums - array of numbers
	* @param {number} target - target sum
	* @returns {number[] \| null} - array containing two indexes or null
	*/

	const twoSum = (nums, target) => {
	for (let i = 0; i < nums.length; i++) {
	for (let j = i + 1; j < nums.length; j++) {
	if (nums[i] + nums[j] === target)
	return [i, j]
	}
	}
	return null
	}

	export { twoSum }

33 changes: 33 additions & 0 deletions Data-Structures/Array/test/TwoSum.test.js

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	import { twoSum } from '../TwoSum'

	describe('twoSum tests', () => {
	it('should return indices for a normal case', () => {
	const nums = [2, 7, 11, 15]
	const target = 9
	expect(twoSum(nums, target)).toEqual([0, 1])
	})

	it('should return indices when pair is in middle', () => {
	const nums = [1, 4, 6, 8, 5]
	const target = 11
	expect(twoSum(nums, target)).toEqual([2, 4])
	})

	it('should handle negative numbers', () => {
	const nums = [-3, 4, 3, 90]
	const target = 0
	expect(twoSum(nums, target)).toEqual([0, 2])
	})

	it('should return null if no pair found', () => {
	const nums = [1, 2, 3, 4]
	const target = 100
	expect(twoSum(nums, target)).toBeNull()
	})

	it('should work with duplicate numbers', () => {
	const nums = [3, 3]
	const target = 6
	expect(twoSum(nums, target)).toEqual([0, 1])
	})
	})

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