Practice/Meta/Leetcode 1. Two Sum

Leetcode 1. Two Sum

CodingMust

Problem

You are given an array of integers and a target integer value. Your task is to locate two different elements in the array that add up to exactly the target value, then return their positions in the array.

You may assume that every input will have exactly one valid answer, and you cannot use the same array element twice (the two indices must be different).

Requirements

1. Return an array containing exactly two indices
2. The two indices must point to different positions in the input array
3. The values at those two indices must sum to the target
4. The order of the returned indices does not matter
5. Exactly one solution is guaranteed to exist for each test case

Constraints

• 2 ≤ nums.length ≤ 10⁴
• -10⁹ ≤ nums[i] ≤ 10⁹
• -10⁹ ≤ target ≤ 10⁹
• Exactly one valid solution exists
• Aim for better than O(n²) time complexity

Examples

Example 1:

Input: nums = [2, 7, 11, 15], target = 9 Output: [0, 1] Explanation: The values at index 0 and index 1 are 2 and 7, which sum to 9.

Example 2:

Input: nums = [3, 2, 4], target = 6 Output: [1, 2] Explanation: The values at index 1 and index 2 are 2 and 4, which sum to 6.

Example 3:

Input: nums = [3, 3], target = 6 Output: [0, 1] Explanation: Both elements have the value 3, and they sum to 6. We return their different indices.