Two Sum Array 232

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] ``` ## Constraints: - `2 <= nums.length <= 10^4` - `-10^9 <= nums[i] <= 10^9` - `-10^9 <= target <= 10^9` - **Only one valid answer exists.**