abs(), labs(), llabs() functions in C/C++

The std::abs(), std::labs() and std::llabs() in C++ are built-in functions that are used to find the absolute value of any number that is given as the argument. Absolute value is the value of a number without any sign. These functions are defined inside the <cmath> header file.

In this article, we will learn how to use std::abs(), std::labs() and std::llabs() in C++.

std::abs()

The std::abs() in C++ is used to find the absolute value of given number. The value returned by std::abs() function is of type int.

Syntax

std::abs(num)

Parameters

• num: Number whose absolute value we have to find.

Return Value

• Returns the absolute value of given number as integer.

Example of std::abs()

abs(22) = 22
abs(-43) = 43

Time Complexity: O(1)
Auxiliary Space: O(1)

Problem with Absolute Values in C++

In C++, integer type ranges from INT_MIN = 2147483647 (considering 32-bit compiler) to INT_MAX = 2147483647. As we can see, converting the INT_MIN to its absolute value will result in a value larger than the max value of the int type. So, it will be returned to its 2's complement. This happens with every integer type whether it's a long int or a long long int. So, it is recommended to check for this case when determining the absolute values for ints.

std::labs()

The std::labs() in C++ is also used to find the absolute value of given number similar to abs() function but it returns the absolute value as long int as compared to int for abs() function.

Syntax

std::labs(num)

Parameters

• num: Number whose absolute value we have to find.

Return Value

• Returns the absolute value of given number as long integer.

Example of std::labs()

labs(227787989) = 27787989
labs(-438989898) = 438989898

Time Complexity: O(1)
Auxiliary Space: O(1)

std::llabs()

The std::llabs() in C++ does the same as abs() and labs() function. It returns the absolute value of given number but in the form of long long integer.

Syntax

llabs(num)

Parameters

• num: Number whose absolute value we have to find.

Return Value

• Returns the absolute value of given number as long long integer.

Example of std::llabs()

llabs(22778798908) = 22778798908
llabs(-43898989878) = 43898989878

Time Complexity: O(1)
Auxiliary Space: O(1)