28. Absolute Value of Integer | Basic I/O

📝 Problem

Given an integer input, print the Absolute value of the input number

Input Format:
Accept an integer as an input.

Output Format:
Positive Integer

Constraints:
-10^5 ≤ input ≤ 10^5

Sample Input 1:

Sample Output 1:

Sample Input 2:

-5

Sample Output 2:

📚

1️⃣ The abs() Function in C++

Simple and Elegant:

📌 Using abs() - No #include needed for integers!

#include <iostream>
using namespace std;

int main() {
    long long a;
    cin >> a;
    cout << abs(a);  // That's it! ✨
    return 0;
}

⚠️ Important Note

For integer types (int, long, long long), abs() is available in <iostream> automatically! You don't need <cmath>.

However, for floating-point types (float, double), you need #include <cmath> and use fabs() or abs().

2️⃣ Visual Understanding

📌 Number Line Visualization:

// Imagine a number line:

    -5  -4  -3  -2  -1   0   1   2   3   4   5
    ◄────────────────┼────────────────►
                     
    // Distance of -5 from 0 = 5 steps
    // Distance of +5 from 0 = 5 steps
    
    abs(-5) = 5  // Same distance!
    abs(5)  = 5

3️⃣ How abs() Works Internally

The Logic Behind abs():

📌 Conceptual Implementation:

// If you were to implement abs() yourself:

int my_abs(int x) {
    if (x < 0)
        return -x;  // Flip the sign
    else
        return x;   // Keep as is
}

// Examples:
// my_abs(-5) → -(-5) → 5 ✓
// my_abs(5)  → 5 ✓
// my_abs(0)  → 0 ✓

💡 Fun Fact

The actual C++ implementation uses bit manipulation for efficiency! But conceptually, it's just checking if negative and flipping the sign.

4️⃣ Different Types, Different Functions

Data Type	Function	Header Required	Example
`int`	`abs()`	`<iostream>`	`abs(-42) → 42`
`long`	`labs()` or `abs()`	`<iostream>`	`abs(-1000L) → 1000`
`long long`	`llabs()` or `abs()`	`<iostream>`	`abs(-5LL) → 5`
`float`	`fabs()` or `abs()`	`<cmath>`	`fabs(-3.14f) → 3.14`
`double`	`fabs()` or `abs()`	`<cmath>`	`abs(-2.718) → 2.718`

5️⃣ Common Use Cases

Where You'll Use Absolute Values:

Distance Calculations: Finding distance between two points
Error Margins: Calculating deviation from expected value
Sorting: Sorting by magnitude, ignoring sign
Game Development: Collision detection, health calculations
Physics Simulations: Speed (magnitude of velocity)
Statistics: Mean absolute deviation, error analysis

📌 Real-World Example - Temperature Difference:

// Finding temperature change magnitude
int morning_temp = -5;  // -5°C
int evening_temp = 10;  // 10°C

int change = abs(evening_temp - morning_temp);
// change = abs(10 - (-5)) = abs(15) = 15°C increase

// Or if it drops:
int night_temp = 2;
change = abs(night_temp - evening_temp);
// change = abs(2 - 10) = abs(-8) = 8°C decrease

6️⃣ Quick Examples

📌 Testing Different Values:

abs(85) = 85      // Positive stays positive
abs(-5) = 5       // Negative becomes positive
abs(0) = 0        // Zero stays zero
abs(-100000) = 100000  // Large negative
abs(42) = 42      // Already positive

                            🎓 Key Takeaway: The abs() function is your go-to 
                            tool for finding absolute values. It's simple, efficient, and handles all the 
                            edge cases for you. For detailed exploration of the cmath library and more 
                            mathematical functions, check out Question #21!
                        

💡 Pro Tip

Modern C++ (C++11 and later) overloads abs() for all types, so you can just use abs() instead of remembering labs(), llabs(), or fabs()!

💻 Solution Code

#include <iostream>

using namespace std;

int main() {
    long long a;
    cin >> a;
    cout << abs(a);
    return 0;
}