/*
 * @lc app=leetcode.cn id=1 lang=cpp
 *
 * [1] 两数之和
 */

// @lc code=start
/*
class Solution
{
public:
    vector<int> twoSum(vector<int> &nums, int target)
    {
        int n = nums.size();
        for (int i = 0; i < n; i++)
        {
            for (int j = i + 1; j < n; j++)
            {
                if (nums[i] + nums[j] == target)
                {
                    return {i, j};
                }
            }
        }
        return {};
    }
};
*/
class Solution
{
public:
    vector<int> twoSum(vector<int> &nums, int target)
    {
        unordered_map<int, int> hashtable;
        for (int i = 0; i < nums.size(); i++)
        {
            auto it = hashtable.find(target - nums[i]);
            if(it != hashtable.end()){
                return {it->second ,i};
            }

            hashtable[nums[i]] = i;
        }
        return {};
    }
};


// @lc code=end