# Ceil and Floor functions in C++

In mathematics and computer science, the floor() and ceil() functions that are defined in <cmath> header file, map a real number to the greatest preceding or the least succeeding integer, respectively.

## C++ floor() Function

The floor() function returns the largest integer that is smaller than or equal to the value passed as the argument (i.e.: rounds down the nearest integer).

### floor() Syntax

`double floor(double x);`

Here x is the floating point value. It returns the largest integer smaller than or equal to x.

Example of the floor of some floating point values:

```Input : 2.5
Output : 2

Input : -2.1
Output : -3```

## CPP

 `// C++ program to demonstrate floor function` `#include ` `#include ` `using` `namespace` `std;`   `// Driver function` `int` `main()` `{` `    ``// using floor function which return` `    ``// floor of input value` `    ``cout << ``"Floor of 2.3 is : "` `<< ``floor``(2.3) << endl;` `    ``cout << ``"Floor of -2.3 is : "` `<< ``floor``(-2.3) << endl;`   `    ``return` `0;` `}`

Output

```Floor of 2.3 is : 2
Floor of -2.3 is : -3
```

## C++ ceil() Function

ceil() function in C++ returns the smallest integer that is greater than or equal to the value passed as the argument (i.e.: rounds up the nearest integer).

### Syntax of ceil()

`double ceil(double x);`

Here x is the floating point value. It returns the smallest integer greater than or equal to x.

Example of ceil of some floating point values:

```Input : 2.5
Output : 3

Input : -2.1
Output : -2```

## C++

 `// C++ program to demonstrate ceil function` `#include ` `#include ` `using` `namespace` `std;`   `// Driver function` `int` `main()` `{` `    ``// using ceil function which return` `    ``// floor of input value` `    ``cout << ``" Ceil of 2.3 is : "` `<< ``ceil``(2.3) << endl;` `    ``cout << ``" Ceil of -2.3 is : "` `<< ``ceil``(-2.3) << endl;`   `    ``return` `0;` `}`

Output

``` Ceil of 2.3 is : 3
Ceil of -2.3 is : -2
```

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

## Difference between ceil() and floor() in C++

Let us see the differences between ceil() and floor() functions in tabular form:

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