Question

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.You may assume that each input would have exactly one solution.
Input: numbers={2, 7, 11, 15}, target=9 Output: index1=1, index2=2

Answer 1

The two-sum problem can be solved using a hash map to efficiently store and look up numbers. The goal is to find two numbers in an array that sum up to a target value and return their indices, with the first index being less than the second.

Step-by-step explanation:

The question is related to a classic problem in the field of computer science and programming, known as the two-sum problem. To solve this, one can utilize a hash map to store and look up numbers efficiently. Here is a conceptual approach to the solution:

1. Initialize an empty hash map.
2. Iterate through each number in the array.
3. For each number, calculate its complement by subtracting it from the target value.
4. Check if the complement exists in the hash map. If it does, the current number and its complement add up to the target value. Return their indices.
5. If the complement is not in the hash map, store the current number and its index in the hash map and continue to the next number.

The result would be returning the indices of the two numbers that add up to the target, ensuring that they are not zero-based and index1 is less than index2, which aligns with your example where numbers = {2, 7, 11, 15}, target = 9, and the output is index1 = 1, index2 = 2.