TwoSum.go

// Source : https://leetcode.com/problems/two-sum/
// Author : Hamza Mogni
// Date   : 2023-05-03

/*****************************************************************************************************
 *
 * 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 <= 10^4
 * 	-10^9 <= nums[i] <= 10^9
 * 	-10^9 <= target <= 10^9
 * 	Only one valid answer exists.
 *
 * Follow-up: Can you come up with an algorithm that is less than O(n^2) time complexity?
 ******************************************************************************************************/

package main

import "fmt"

func twoSum(nums []int, target int) []int {
	visited := make(map[int]int)

	for idx, num := range nums {
		searching := target - num

		visited_idx, ok := visited[searching]
		if ok {
			return []int{idx, visited_idx}
		}

		visited[num] = idx
	}

	return []int{}
}

func main() {
	fmt.Println(twoSum([]int{2, 7, 11, 15}, 9))
	fmt.Println(twoSum([]int{3, 2, 4}, 6))
	fmt.Println(twoSum([]int{3, 3}, 6))

}