Two Sum
easy
Two Sum
easyhash-maparray
Given an array of integers `nums` and an integer `target`, return indices of the two numbers such that they add up to `target`. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order.
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]
Explanation: Because nums[0] + nums[1] == 6, we return [0, 1].
Constraints:
- 2 <= nums.length <= 10⁴
- -10⁹ <= nums[i] <= 10⁹
- -10⁹ <= target <= 10⁹
- Only one valid answer exists.
Follow-up: Can you come up with an algorithm that is less than O(n²) time complexity?
Sketch your plan
How would you attack this — even a rough or slow idea?
No need to be clever or even right. Just put down where you'd start — it primes you for the solution.
Put down any starting idea.