201. Two Sum
Easy
Hash Map Lookup
Array
Problem
Given an array of integers nums and an integer target, return the indices of the two numbers such that they add up to target. You may assume that each input has exactly one solution, and you may not use the same element twice. You can return the answer in any order.
Examples
Example 1
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Because nums[0] + nums[1] == 9.
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
� Exactly one valid answer exists.
Hints
?? A brute-force solution checks every pair.
?? Can you remember values you have already seen?
?? For each number x, look for target - x.
Expected Complexity
Time: O(n)
Space: O(n)
Follow-up
Can you solve the problem in O(n) time?
Practice Notes
Attempts: 0
Time spent: 0min
Hints used: 0
JavaScript
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Case 1
Case 2
Case 3
Input
[2,7,11,15], 9Expected
[0,1]