# c++ sort numbers by magnitude/absolute value

To sort numbers by magnitude or absolute value in C++, you can follow these steps:

- Include the necessary header files:

```
#include <iostream>
#include <algorithm>
#include <cmath>
```

The `<iostream>`

header file is required for input/output operations, `<algorithm>`

is needed for sorting functions, and `<cmath>`

for the absolute value function.

- Define a comparison function:

```
bool compareByMagnitude(int a, int b) {
return std::abs(a) < std::abs(b);
}
```

This function takes two integers `a`

and `b`

as parameters and compares their absolute values using the `std::abs()`

function. It returns `true`

if the absolute value of `a`

is less than the absolute value of `b`

, and `false`

otherwise.

- Use the comparison function with the sorting algorithm:

```
int main() {
int numbers[] = { -5, 10, -3, 8, -1, 0 };
int size = sizeof(numbers) / sizeof(numbers[0]);
std::sort(numbers, numbers + size, compareByMagnitude);
for (int i = 0; i < size; i++) {
std::cout << numbers[i] << " ";
}
return 0;
}
```

In this example, we have an array of numbers. The `std::sort()`

function is used to sort the array in ascending order based on the absolute value of each element. The `compareByMagnitude`

function is passed as the third parameter, which specifies the custom comparison logic.

- Output the sorted numbers:

```
Output: 0 -1 -3 5 8 10
```

The sorted array is printed using a loop, and the numbers are separated by spaces.

By following these steps, you can successfully sort numbers by magnitude/absolute value in C++.