Coding Interview Prep: Two Sum Question — 2 Solutions in JavaScript

Prompt

Solution 1: Brute Force Method

Complexity: O(n²)

• U

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */

//O(n^2) brute force method
var twoSum = function(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 new Array(i, j);
            }
        }
    }
    return [];
};

Solution 2: Hash Map

Complexity: O(n)

• Use a memory to keep data for something to improve time complexity. Here we will use a Hash Map.
• ‘n’ is the number of elements in input array. In the worst case, we put all numbers in map.
• A map object holds key-value pairs and remembers the original insertion order of the keys. Any value (both objects and primitive values like string, number and boolean ) may be used as either a key or a value.
• A key in the Map may only occur once. It is unique in the Map’s collection.

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target){…