Leetcode - Two Sum - Solution
1 min read

Leetcode - Two Sum - Solution

Leetcode - Two Sum - Solution

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] 
Output: 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]

Constraints:

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

Solution in Python

from collections import defaultdict
class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        d = defaultdict(list)

        for index,value in enumerate(nums):
            d[value].append(index)

        for number in d:
            second_number = target-number
            if number*2==target:
                if len(d[number])==2:
                    return d[number]
            elif second_number in d :
                return d[number]+d[second_number]

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