leetcode-167-two-sum-II-input-array-is-sorted.swift

/**

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https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/


Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2.

Note:

Your returned answers (both index1 and index2) are not zero-based.
You may assume that each input would have exactly one solution and you may not use the same element twice.
Example:

Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

*/

/**
Big O Annotation
Time complexity O(n) where n is the amount of elements in nums.
Space complexity O(n) where n is the amount of elements in nums.
*/
func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
	
    /**
    Creating a map for every element in nums
    with their respecitve indices.
    */
    var map: [Int: Int] = [:]

    // Iterate through nums
    for (index, element) in nums.enumerated() {
    
        /**
        Check if we have a mapped element can be
        created when substracting the current target
        with the current element
        */
        if let mapped = map[target - element] {
        
            // And return their indices each +1
            return [mapped + 1, index + 1]
        }
    
        // Add the current element to the map
        map[element] = index
    }

    return []
}