Back to ArraysTwo Sum
Easy

Two Sum

EasyMust DoHashing

Given an array of integers and a target, return the indices of the two numbers that add up to the target. Exactly one valid pair is guaranteed to exist.

Examples

Example 1

Input:
nums = [2,7,11,15], target = 9
Output:
[0,1]

Explanation: nums[0] + nums[1] == 9, so we return their indices [0, 1].

Example 2

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

Explanation: nums[1] + nums[2] == 6.

Example 3

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

Constraints

  • 2 <= nums.length <= 10^4
  • -10^9 <= nums[i] <= 10^9
  • -10^9 <= target <= 10^9
  • Only one valid answer exists.

Follow-up

Can you come up with an algorithm that runs in less than O(n^2) time complexity?

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