Values Appearing Alone Without Consecutive Neighbors
Company: Apple
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
### Problem
A value `x` is lonely if it occurs exactly once in `nums` and neither `x - 1` nor `x + 1` occurs anywhere in the array. Return every lonely value, in any order. These are neighboring integer values, not neighboring array positions.
```cpp
class Solution {
public:
vector<int> findLonely(vector<int>& nums);
};
```
### Examples
**Example 1:**
```text
nums = [0,2,2,5]
Output: [0,5]
Explanation: Each occurs once without a numerical neighbor; 2 is repeated.
```
**Example 2:**
```text
nums = [4,5,8]
Output: [8]
Explanation: 4 and 5 disqualify each other, while 8 stands alone.
```
### Constraints
- `1 <= nums.length <= 10^5`.
- `0 <= nums[i] <= 10^6`.
### Clarifying Questions
Repeated values never qualify. No order is imposed on the result.
```hint Inspect the structure
What information is lost by using only a set of present values?
```
### What a Strong Answer Covers
- Require exactly one occurrence and check both neighboring integer values.
- Return every qualifying value once while allowing any output order.
- Handle zero, repeated values and separated array positions containing consecutive values.
### Follow-up Questions
How could already sorted input support the same checks?
Overview: Values Appearing Alone Without Consecutive Neighbors. A value x qualifies when it appears exactly once in nums and neither x-1 nor x+1 appears anywhere. Return all qualifying values in any order. Numerical neighbors matter, not adjacency of array positions.