法一：暴力求解

class Solution
{
public:
    vector<int> twoSum(vector<int> &nums, int target)
    {
        int n = nums.size();
        for (int i = 0; i < n; i++)
        {
            // 第⼀层循环从前往后列举第⼀个数
            for (int j = i + 1; j < n; j++)
            {                                    // 第⼆层循环从 i 位置之后列举第⼆个数
                if (nums[i] + nums[j] == target) // 两个数的和等于目标值 已经找到结果
                    return {nums[i], nums[j]};
            }
        }
        return {-1, -1};
    }
};

对撞指针：思路和上篇一致

class Solution
{
public:
    vector<int> twoSum(vector<int> &nums, int target)
    {
        int left = 0, right = nums.size() - 1;
        while (left < right)
        {
            int sum = nums[left] + nums[right];
            if (sum > target)
                right--;
            else if (sum < target)
                left++;
            else
                return {nums[left], nums[right]};
        }

        return {-1, -1};
    }
};