How to optimize this LeetCode solution for Two Sum

[codechallenger000]

I’m working on the classic Two Sum problem from LeetCode:

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

Here’s my current solution in Python:

def twoSum(nums, target):
    for i in range(len(nums)):
        for j in range(i+1, len(nums)):
            if nums[i] + nums[j] == target:
                return [i, j]

[SpringStar-dev]

You’re right that your current solution is O(n²) because it checks every pair.
A more optimal approach is to use a hash map (dictionary) so you can check in constant time if the complement exists.

Here’s the Python version:

def twoSum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        complement = target - num
        if complement in seen:
            return [seen[complement], i]
        seen[num] = i

[codechallenger000]

thanks for your help

[codechallenger000]

thanks for your help