LeetCode 1.Two Sum (Easy) - Kotlin

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.

 

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?

 

 

해결

class Solution {
    fun twoSum(nums: IntArray, target: Int): IntArray {
        val map = mutableMapOf<Int, Int>() // 숫자와 인덱스를 저장할 해시맵 

        for (i in nums.indices) { # 순회할때 사용 > indices
            val complement = target - nums[i]

            if (map.containsKey(complement)) {
                return intArrayOf(map[complement]!!, i)
            }

            map[nums[i]] = i
        }

        return intArrayOf()
    }
}