Can anyone explain me this question: Two Sum

[bibhutigswain]

Can anyone explain me this Two Sum DSA question

[bibhutiswain9]

I also have same question @bibhuti9

[bibhuti9]

The given problem is attempting to solve the classic "Two Sum" problem using JavaScript. In the "Two Sum" problem, you are given an array of integers (nums) and a target integer (target). Your goal is to find two different indices in the array such that the numbers at those indices add up to the target. You should return these indices in an array.

Here’s the provided code and an explanation of why it doesn’t work as intended:

var twoSum = function (nums, target) {
    let numIndices = {};  // Create a hash map to store the indices of elements
    for (let i = 0; i < nums.length; i++) {
        let complement = target - nums[i];  // Calculate the complement
        if (numIndices.hasOwnProperty(complement)) {  // Check if complement exists in hash map
            return [numIndices[complement], i];  // Return the indices if found
        }
        numIndices[nums[i]] = i;  // Store the index of the current element in the hash map
    }
    return [];  // Return an empty array if no solution is found
};

var nums = [3, 2, 4], target = 6;
console.log(twoSum(nums, target));  // Output: [1, 2]

Explanation

Initialization: We initialize an empty object numIndices to store the indices of the elements.

Iterate through the array: We loop through each element in the array nums.

Calculate complement: For each element, we calculate the complement (i.e., target - nums[i]).

Check for complement: We check if the complement exists in the hash map numIndices. If it does, we return the indices of the complement and the current element.

Store the current element index: If the complement does not exist, we store the index of the current element in the hash map.

Return result: If we find a pair that sums up to the target, we return their indices. If no such pair is found, we return an empty array.

This approach ensures that we find the indices efficiently with a time complexity of
𝑂
(
𝑛
)
O(n), where
𝑛
n is the length of the input array nums.