C++ Vector Size

To get the size of a C++ Vector, you can use size() function on the vector.

size() function returns the number of elements in the vector.

Example 1: Find Vector Length using size()

In the following C++ program, we define a vector of integers, add some elements to it, and then find its length using size() function.

C++ Program

#include <iostream>
#include <vector>
using namespace std;

int main() {
   vector<int> nums;
   nums.push_back(24);
   nums.push_back(81);
   nums.push_back(57);

   cout << nums.size();
}

Output

3

Example 2: Length of Empty Vector

In the following C++ program, we define a vector of integers, with no elements in it, and then find its length using size() function. size() should return a value of zero.

C++ Program

#include <iostream>
#include <vector>
using namespace std;

int main() {
   vector<int> nums;
   cout << nums.size();
}

Output

0

Example 3: Length of Vector using Foreach

You can also use C++ Foreach statement to get the length of size of a vector.

In the following program, we shall define a vector and initialize with elements. Then take a len variable with zero initial value that acts as a counter to count the number of elements in the vector. Use Foreach statement to iterate over the elements of vector and increment the counter during each iteration.

C++ Program

#include <iostream>
#include <vector>
using namespace std;

int main() {
   vector<int> nums;
   nums.push_back(24);
   nums.push_back(81);
   nums.push_back(57);

   int len = 0;
   for (int element: nums)
      len++; 

   cout << len;
}

Output

3

Conclusion

In this C++ Tutorial, we learned to find the size of vector, which is the number of elements in a vector using builtin functions or statements like foreach.