Subarray of Given Sum in Swift

Given an array of integers and a number target, find a continous subarray whose sum is equal to target.

Return the start and end indices denoting this subarray. If there are multiple solutions, you can return any of them.

Example:

Input: nums = [1, 1, 5, 2, 1, 3, 10, 2, 1], k = 21
Output: [2, 6]
Explanation: 5 + 2 + 1 + 3 + 10 = 21

1. The array can consist of positive and negative numbers.

2. Your algorithm should run in O(n) time and use O(n) extra space.