Two Sum Problem

Problem Description

Given an array of integers nums and an integer target, your task is to return the indices of the two numbers in the array such that they add up to the target value.

• You may assume that each input will have exactly one solution.
• You may not use the same element twice.
• The solution can be returned in any order.

Examples

Example 1:

Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

Example 2:

Input: nums = [3, 2, 4], target = 6
Output: [1, 2]

Example 3:

Input: nums = [3, 3], target = 6
Output: [0, 1]

Constraints:

• The number of elements in the array is between 2 and 10^4.
• Each element in the array nums[i] is an integer where:
  • ( -10^9 \leq nums[i] \leq 10^9 )
• The target is an integer where:
  • ( -10^9 \leq target \leq 10^9 )
• Only one valid answer exists.

Follow-Up Question:

Can you come up with an algorithm that runs in less than O(n²) time complexity?

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