In this C++ tutorial, you shall learn about vector of vectors, how to create vector of vectors, and traverse the inner vectors using For loop, with example programs.

## Vector of Vectors in C++

Vector of vectors is a vector in which each element is a vector of elements.

To create a vector of vectors, we need to specify the datatype of element as `vector<>`, and specify vectors as elements, as shown in the following.

```//int vectors
vector<int> v1 { 1, 3, 5, 7, 9 };
vector<int> v2 { 2, 4, 6, 8, 10 };

//vector of vectors
vector<vector<int>> vv = {v1, v2};```

## Examples

### 1. Vector of Integer Vectors

In the following program, we take two integer vectors in `v1` and `v2`, and use them to create a vector of integer vectors `vv`.

main.cpp

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

int main() {
//int vectors
vector<int> v1 { 1, 3, 5, 7, 9 };
vector<int> v2 { 2, 4, 6, 8, 10 };

//vector of vectors
vector<vector<int>> vv = {v1, v2};

//iterate over vector elements
for (auto& tempVector : vv) {
for (auto& element : tempVector) {
cout << element << "  ";
}
cout << endl;
}
}```

Output

```1  3  5  7  9
2  4  6  8  10```

## Conclusion

In this C++ Tutorial, we learned how to define a vector of vectors, and how to traverse through individual elements of the inner vectors.