Out of range error when reading from vector

Question

After reading integers from a txt file and push_back them to a vector for different txt files (all of same structure) i dont get the right result every time.

the first line (first number of the vector) show how many graphs are to be implemented from this file. Then the first number of the second line (second number of the vector) gives the nodes and the second number of the second line (third number of the vector) the edges. After there are the edges number pairs, then again number of nodes and number of edges and so on.

For the first vector my code works. This is what i have written:

int main(int argc, char** argv)  { 
vector<int> read_ints = {2,9,9,6,3,7,1,8,9,6,4,5,1,1,9,2,5,1,4,5,4,9,9,4,6,8,1,3,4,2,8,6,7,9,3,4,7,1,5,4,9};
vector<int> read_ints2 = {10,25, 18,5 ,19,4 ,23,13, 25,4 ,7,2 ,18,11, 4,15, 25,16, 12,2 ,23,5 ,23,24, 19,14, 11,2 ,24,19, 2,14, 16,20, 24,19, 8,18, 3,15, 15,14, 10,15, 4,8 ,10,2 ,3,6 ,11,13, 9,8 ,1,7 ,13,5 ,12,3 ,9,12, 7,1 ,5,15, 2,14, 11,4 ,6,17, 17,9 ,1,10, 17,5 ,11,5 ,14,14, 13,7 ,4,14, 4,10, 8,17, 4,9 ,3,5 ,16,6 ,16,10, 3,2 ,14,1 ,13,15, 17,16, 13,16, 16,6 ,1,13, 5,5 ,8,16, 1,7 ,13,13, 10,10, 3,8 ,14,3 ,2,7 ,5,11, 12,7 ,12,7 ,10,15, 4,13, 15,11, 16,22, 22,11, 13,17, 6,10, 7,8 ,10,10, 21,20, 5,2 ,20,14, 4,3 ,22,7 ,1,4 ,19,2 ,16,11, 8,15, 1,1 ,4,16, 19,9 ,16,11, 3,12, 5,6 ,22,9 ,2,17, 5,18, 18,10, 4,10, 13,3 ,10,17, 12,15, 6,11, 2,6 ,17,7 ,5,14, 16,8 ,2,7 ,8,3 ,1,16, 9,16, 1,14, 12,9 ,5,14, 9,18, 11,20, 20,11, 8,9 ,11,1 ,19,7 ,15,5 ,12,1 ,6,10, 4,2 ,19,20, 7,3 ,8,11, 13,5 ,9,20, 18,10, 16,4 ,6,17, 14,18, 19,17, 5,8 ,10,17, 15,12, 12,6 ,4,12, 2,12, 8,7 ,4,7 ,5,10, 8,1 ,5,1 ,2,10, 6,10, 3,8 ,9,9 ,11,8 ,8,5 ,3,7 ,8,6 ,4,7 ,1,2 ,6,8 ,2,3 ,4,5 ,1,20, 20,6 ,15,14, 7,4 ,17,13, 3,8 ,15,17, 8,12, 18,14, 18,18, 7,9 ,15,11, 5,9 ,8,2 ,20,16, 20,4 ,1,3 ,2,20, 3,14, 10,1 ,5,19, 13};
vector<int>::iterator ints_iter;
int counter = 0; // to count the edges, for testing purposes.
int num_of_graphs = read_ints.at(0);
int num_vertices = read_ints.at(1) + 1; // + 1 because of the code i wrote for implementing the graph's vertices
int num_edges = read_ints.at(2);
read_ints.erase(read_ints.begin(), read_ints.begin() + 3); // deleting the first line (number of graphs) and the first graph's info, so it is easier to add edge's pairs.
for (int i = 0; i < num_of_graphs; i++){
    Graph g(num_vertices); // Graph is the class i made
    for (int i = 0; i < num_edges * 2; i += 2) {
        cout << read_ints.at(i) << " " << read_ints.at(i + 1) << endl; // printing the pairs line by line
        counter++;
    }
    read_ints.erase(read_ints.begin(), read_ints.begin() + (num_edges * 2)); // delete the pairs of the i'th graph every time from the vector to add the new edges on the next graph
    if (read_ints.empty()) // error handling for the last graph (which doesnt work)
        break;
    else 
        int num_vertices = read_ints.at(0) + 1; // after deleting the previous graph info and the previous graphs edges from the vector, i change the i values for next graph's nodes and edges
        int num_edges = read_ints.at(1);
        read_ints.erase(read_ints.begin(), read_ints.begin() + 2); // since the vector is not empty i erase the last elements
}
cout << counter;

return 0;

For the first vector it works but for a bigger one like the second it says "terminate called after throwing an instance of 'std::out_of_range' what(): vector::_M_range_check: __n (which is 8) >= this->size() (which is 8)"

after printing out all the edges.

Better yet, why did you post the image, instead of taking your program and assigning the data directly in the variables? There isn't a need for input statements or file input -- take the test data, and set the vector(s) to the test values. — PaulMcKenzie, Apr 24 '20 at 01:16
Why must we go to an external link for the test data? That link goes away, the question becomes meaningless. — PaulMcKenzie, Apr 24 '20 at 01:27
@PaulMcKenzie the reason that i want to read from the txt file is that this is what the excercise asks. I can do that one by one and creating the graph but then for the other txt files that are huge i cant post that pice of code. (maybe i didint fully understand your comment, sorry) — george_pap, Apr 24 '20 at 01:28
So we have to create a file to run your program? [Look at this](http://coliru.stacked-crooked.com/a/17aaf09d85791580). That is how you could have presented your original example. — PaulMcKenzie, Apr 24 '20 at 01:30
@PaulMcKenzie ok i will edit the code to crete 3 vectors for each txt file's data. — george_pap, Apr 24 '20 at 01:30
No, you didn't *fix that*, you provided a link to a text file. Edit your post and add the information **here**, in the question itself, so that it's available as part of the question. Expecting us to go elsewhere to do iwnload it isn't reasonable, and all information needs to be in the question so that it's available to future site users. Copy and paste the **content** of the text file into your question here and format it so that it's readable, just like the code. — Ken White, Apr 24 '20 at 01:31
@KenWhite it took some minutes, now i edited it, again sorry. i didnt provide the 3rd vecotr because it had 3000+ lines) — george_pap, Apr 24 '20 at 01:42

score 0 · Accepted Answer · answered Apr 24 '20 at 01:04

This

    else 
        int num_vertices = read_ints.at(0) + 1;
    int num_edges = read_ints.at(1);
    read_ints.erase(read_ints.begin(), read_ints.begin() + 2);

declares two local variables named num_vertices and num_edges. These are different from the local variables of the same name declared earlier in main, so the values used on the next iteration of the loop are from the first block of data.

Note that I've also adjusted the indentation to show the how the statements interact with the else. In this case it is harmless because the other branch of the if is a break but you need to be careful that you don't misread your code due to misleading indentation.

after hours of writing this i didnt realize that i was declaring 2 new variables. I just deleted "int" so that was referring to the variables of the main block.Silly mistake, but could happen. Thanks again! — george_pap, Apr 24 '20 at 02:07

Out of range error when reading from vector

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