how to pushback on a vector of vectors?

Question

I am taking 20 lines of input. I want to separate the contents of each line by a space and put it into a vector of vectors. How do I make a vector of vectors? I am having have struggles pushing it back... My input file: ``` Mary had a little lamb lalala up the hill the sun is up ``` The vector should look like something like this. ``` ROW 0: {"Mary","had", "a","little","lamb"} ROW 1: {"lalala","up","the","hill"} ``` This is my code.... ``` string line; vector > big; string buf; for (int i = 0; i < 20; i++){ getline(cin, line); stringstream ss(line); while (ss >> buf){ (big[i]).push_back(buf); } } ```

Accepted Answer

The code is right, but your vector has zero elements in it so you cannot access `big[i]`.

Set the vector size before the loop, either in the constructor or like this:

```
big.resize(ruleNum);
```

Alternatively you can push an empty vector in each loop step:

```
big.push_back( vector<string>() );
```

You don't need the parentheses around `big[i]` either.

how to pushback on a vector of vectors?

Solution

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