# Computing an inner product of tuples represented as vectors : vector « vector « C++ Tutorial

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

int main()
{
const long N = 600000; // Length of tuples x and y
const long S = 10;     // Sparseness factor

vector<double> x(N), y(N);

for (long k = 0; 3 * k * S < N; ++k)
x[3 * k * S] = 1.0;
for (long k = 0; 5 * k * S < N; ++k)
y[5 * k * S] = 1.0;

double sum = 0.0;
for (long k = 0; k < N; ++k)
sum += x[k] * y[k];

cout << sum << endl;
return 0;
}
```
`4000`
 16.1.vector 16.1.1. Demonstrating the simplest STL vector constructors: duplicate chars 16.1.2. Demonstrating the simplest STL vector constructors: empty vector 16.1.3. Use generic vector to create vector of chars 16.1.4. Use generic vector to create vector of integers 16.1.5. creates a vector of ints with zero elements 16.1.6. creates a vector of 10 ints with value 100 16.1.7. Use generic vector to create vector of strings 16.1.8. The Instantiation of vector 16.1.9. Using the vector 16.1.10. get an iterator that points to the maximum with max_element 16.1.11. Assign elements in int array to vector 16.1.12. Store a class object in a vector 16.1.13. Read keyboard input to a vector 16.1.14. Add class to a vector and then delete them one by one 16.1.15. Pass vector to a function 16.1.16. Computing an inner product of tuples represented as vectors 16.1.17. Assign value to the last element 16.1.18. Demonstrating STL vector copying constructors 16.1.19. Instantiate one vector and initialize it to the contents of another 16.1.20. Demonstrating STL vector constructors with a user-defined type and showing copying explicitly 16.1.21. Vector Init Array 16.1.22. Demonstrating STL vector constructors with a user-defined type