:
: https://reurl.cc/lQeDQj
:
: 2441. Largest Positive Integer That Exists With Its Negative
:
: 給定一不包含0的數列，尋找最大正整數，此正整數k的-k需存在於nums
:
: 回傳正整數k 如果無符合條件的正整數 回傳-1
:
: Example 1:
:
: Input: nums = [-1,2,-3,3]
: Output: 3
: Explanation: 3 is the only valid k we can find in the array.
婷婷：可不可以用unordered map
其實用set也可以捏
反正只是記錄而已
捏
```cpp
class Solution {
public:
int findMaxK(vector<int>& nums)
{
int res = -1;
int len = nums.size();
unordered_set<int> paper;
for(int k : nums)
{
if(paper.find(-k) != paper.end())res = max(res,abs(k));
paper.insert(k);
}
return res;
}
};
```