# Leetcode 1. Two Sum

[easy][Amazon]

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 = 9Output: [0,1]Output: Because nums[0] + nums[1] == 9, we return [0, 1].`

Example 2:

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

Example 3:

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

Constraints:

• `2 <= nums.length <= 103`
• `-109 <= nums[i] <= 109`
• `-109 <= target <= 109`
• Only one valid answer exists.

[Gary-brute force]

1. create two loop to find the target

[HashMap]

1. using hashmap to note every target index
2. TC: O(n)

CS new grad, 6 years experience related to supply chain management. Located in Bay area

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CS new grad, 6 years experience related to supply chain management. Located in Bay area