C++ Vector Library - empty() Function


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Description

The C++ function std::vector::empty() tests whether vector is empty or not. Vector of size zero is considered as empty vector.

Declaration

Following is the declaration for std::vector::empty() function form std::vector header.

C++98

bool empty() const;

C++11

bool empty() const noexcept;

Parameters

None

Return value

Returns true if vector is empty otherwise false.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::vector::empty() function.

#include <iostream>
#include <vector>

using namespace std;

int main(void) {
   vector<int> v;

   if (v.empty())
      cout << "Vector v1 is empty" << endl;

   v.push_back(1);
   v.push_back(2);
   v.push_back(3);

   if (!v.empty())
      cout << "Vector v1 is not empty" << endl;

   return 0;
}

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

Vector v1 is empty
Vector v1 is not empty
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