# C++ Algorithm Library - lexicographical_compare() Function

#### Complete Python Prime Pack for 2023

9 Courses     2 eBooks

#### Artificial Intelligence & Machine Learning Prime Pack

6 Courses     1 eBooks

#### Java Prime Pack 2023

8 Courses     2 eBooks

## Description

The C++ function std::algorithm::lexicographical_compare() tests whether one range is lexicographically less than another or not. A lexicographical comparison is the kind of comparison generally used to sort words alphabetically in dictionaries.

## Declaration

Following is the declaration for std::algorithm::lexicographical_compare() function form std::algorithm header.

### C++98

```template <class InputIterator1, class InputIterator2>
bool lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2);
```

## Parameters

• first1 − Input iterator to the initial position of the first sequence.

• last1 − Input iterator to the final position of the first sequence.

• first2 − Input iterator to the initial position of the second sequence.

• last2 − Input iterator to the final position of the second sequence.

## Return value

Returns true if one range is lexicographically less than second otherwise returns false.

## Exceptions

Throws exception if either the element comparison or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

## Time complexity

2 * min(N1, N2) , where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).

## Example

The following example shows the usage of std::algorithm::lexicographical_compare() function.

```#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

using namespace std;

int main(void) {
vector<string> v1 = {"One", "Two", "Three"};
vector<string> v2 = {"one", "two", "three"};
bool result;

result = lexicographical_compare(v1.begin(), v1.end(), v2.begin(), v2.end());

if (result == true)
cout << "v1 is less than v2." << endl;

v1[0] = "two";

result = lexicographical_compare(v1.begin(), v1.end(), v2.begin(), v2.end());

if (result == false)
cout << "v1 is not less than v2." << endl;

return 0;
}
```

Let us compile and run the above program, this will produce the following result −

```v1 is less than v2.
v1 is not less than v2.
```
algorithm.htm