[LeetCode][C++] #1. Two Sum

[Easy][Question]:

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]
Output: 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 <= 103
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

My Solution[C++]:

[Ideas]: 先用unordered_map存每一次的數字，key為數字，value為第幾個。接著用unordered_map.find去找有沒有對應的數字，若沒有的話會回傳.end()

Map.find(target — nums[i]) != Map.end()

若沒找到，就繼續丟盡Map裡面

Map[nums[i]] = i;