Question

How to resize a vector of vector containing integer values.

std::vector<std::vecotr<int>> MyVector;
int value = 10;

//need to insert values as 2 rows and 3 columns, like
//Myvector[0][0] = value;
//Myvector[0][1] = value;
//Myvector[0][2] = value;
//Myvector[1][0] = value;
//Myvector[1][1] = value;
//Myvector[1][2] = value;

// ......
//here i have to resize the vector size to 4 rows and 5 cols using resize() function.

MyVector.resize(.......); //Hoe is this possible.

The first problem is , I have to insert the values as 2 rows and 3 columns. how can I use push_back function for this purpose. After that need to resize to the specified size. Since it a vector of vector I am getting worried about this.

Answer 1

You can think of a vector of vectors as a matrix where the member vectors are “rows”.

int main()
{
    std::vector<std::vector<int> > MyVector;
    //Create a row:
    std::vector<int> subVector;
    subVector.push_back(1);
    subVector.push_back(2);
    //put the row into the vector:
    MyVector.push_back(subVector);
    //create another row:
    subVector.clear();
    subVector.push_back(3);
    subVector.push_back(4);
    //put the second row into the vector
    MyVector.push_back(subVector);
    //access the first row and add an element to it:
    MyVector[0].push_back(6);
    //access the second row and add an element to it:
    MyVector[1].push_back(6);
}