[LeetCode] Two Sum

문제

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.

 

예시

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]

 

제한

• 2 <= nums.length <= 104
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

 

Two Sum - LeetCode

 

풀이

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        for i in range(len(nums)):
            for j in range(i+1, len(nums)):
                if nums[i] + nums[j] == target:
                    return i, j

 

다른풀이 - 해시테이블 사용

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        hashtable = {}
        for i in range(len(nums)):
            comp = target - nums[i]
            if comp in hashtable:
                return i, hashtable[comp]
            hashtable[nums[i]] = i