Find the Largest Positive Value with a Negative Counterpart
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
In nonzero integer array `nums`, find the greatest positive integer `k` for which both `k` and `-k` appear. Return `k`, or `-1` if no such pair of values exists.
```cpp
class Solution {
public:
int findMaxK(vector<int>& nums);
};
```
### Examples
**Example 1:**
```text
Input: nums = [-5,5,2,-2,9]
Output: 5
Explanation: Magnitudes2 and 5 have both signs, while9 lacks-9.
```
**Example 2:**
```text
Input: nums = [-4,7,1]
Output: -1
Explanation: No value has its opposite sign present.
```
### Constraints
- `1 <= nums.length <= 1000`.
- `-1000 <= nums[i] <= 1000`, and no entry is 0.
### Clarifying Questions
- Is the result positive when a pair exists? Yes.
- Can two copies of the same sign form a pair? No; both signs must appear.
- Can zero appear? No.
- Does occurrence order matter? No.
```hint Check the boundary
Check a duplicated positive value whose negative is absent.
```
Overview: Find the largest positive array value that also has its negative present, returning -1 when no such value exists.