Check the Sum of Proper Positive Divisors
Company: Amazon
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
A positive integer is perfect when the sum of all its positive divisors smaller than itself equals the integer. Return whether num has this property.
```cpp
class Solution {
public:
bool checkPerfectNumber(int num);
};
```
### Examples
**Example 1:**
```text
num = 6
Output: true
Explanation: Its proper divisors are 1, 2 and 3, whose sum is 6.
```
**Example 2:**
```text
num = 12
Output: false
Explanation: 1+2+3+4+6 = 16.
```
### Constraints
- The input num is an integer from 1 through 100000000.
### Clarifying Questions
Exclude the number itself and avoid counting a square-root divisor twice.
```hint Read the boundary condition
How can factor pairs replace scanning every smaller positive integer?
```
### Contract considerations
Exclude the number itself and avoid counting a square-root divisor twice.
Overview: Check the Sum of Proper Positive Divisors. A positive integer is perfect when the sum of all its positive divisors smaller than itself equals the integer.
