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1. Two Sum

Array Hash Table

Problem - Two Sum

Easy

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

 

Follow-up: Can you come up with an algorithm that is less than O(n2) time complexity?

Solutions

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/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    let out = []
    for (let i = 0; i < nums.length; i++){
        for (let j = 0; j < nums.length; j++){
            if (nums[i] + nums[j] == target && i != j){
                console.log('[' +i + ',' + j + ']')
                out[0] = i
                out[1] = j
                return out

            }
        }
    }
    return out
};

Submission Stats:

  • Runtime: 192 ms (5.33%)
  • Memory: 44.2 MB (100.00%)
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class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        done = {}

        for i, x in enumerate(nums):
            search_val = target - x
            if search_val in done:
                return done[search_val], i

            done[x] = i

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 19 MB (23.71%)