Trying to read strings from a file into an unsigned char vector

Question

I'm really new to coding yet, so bear with me. When running the following code, I always get a fatal error:

Debug Assertion Failed!
Program: [program name]
File: [MS VS path]\include\vector
Line: 1502

Expression: vector subscript out of range

What could be causing this?

string temp1;
stringstream temp2;
unsigned char temp3;
vector<vector<unsigned char>>vectorname;
        for (unsigned int i = 0; i < 5; i++) {
            for (unsigned int j = 0; j < 5; j++) {
                Datei >> temp1; // copies file into string
                temp2 << temp1; //copies string into streamstring
                temp2 >> temp3; //copies streamstring into unsigned char
                vectorname[i][j] = temp3 //sets the unigned char as value at the i,j, position.

            }
        }

Answer 1

To dynamically grow the 2D vector in the loop, you need to add a new inner vector, and given the new inner vector, add items to it.

Here is an example:

#include <vector>
int main()
{
    std::vector<std::vector<unsigned char>> vectorname;
    for (unsigned int i = 0; i < 5; i++) 
    {
        // add a new vector to the outer std::vector
        vectorname.push_back(vector<unsigned char>());

        // now add data to the newly added vector. The `back()` returns
        // a reference to the last added vector
        for (unsigned int j = 0; j < 5; j++) {
            vectorname.back().push_back(j);    
    }
}