Array After Simultaneous Local-Extremum Updates
Company: Virtu Financial
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
Each day, use the previous day's whole array to update every interior element simultaneously: increase it by 1 if strictly smaller than both neighbors, decrease it by 1 if strictly larger than both, and otherwise leave it. Endpoints never change. The source states the process eventually stops changing. Return that final array.
```cpp
class Solution {
public:
vector<int> transformArray(vector<int>& arr);
};
```
### Examples
**Example 1:**
```text
Input: arr = [1,4,1]
Output: [1,1,1]
Explanation: The center changes4->3->2->1 over three days, then is no longer a strict maximum.
```
**Example 2:**
```text
Input: arr = [3,1,2]
Output: [3,2,2]
Explanation: The center increases once, after which equality with its right neighbor prevents another update.
```
### Constraints
- The array contains 3 to 100 integers.
- Each original value is in `[1,100]`.
### Contract considerations
The return type is the original vector result; simultaneous daily evolution is part of the contract.
```hint Read the boundary condition
When an interior value equals either neighbor, do the strict-extremum rules require it to change?
```
### Boundary reminders
The return type is the original vector result; simultaneous daily evolution is part of the contract.
Overview: Array After Simultaneous Local-Extremum Updates. Each day, use the previous day's whole array to update every interior element simultaneously: increase it by1 if strictly smaller than both neighbors, decrease it by1 if strictly larger than both, and otherwise leave it.