2D字符串向量的cout仅打印最后一行

Question

I'm reading a text file and loading to a std::vector<std::string> course and when I attempt to print it based on course.size() and course[i].size it only prints the last line.

Here is the code:

int main(int argc, char** argv) {
    ifstream fin(argv[1]);
    vector<string> course;
    string line;

    while (getline(fin, line)) {
        course.push_back(line);
    }

    for (int i = 0; i < course.size(); i++) {
        for (int j = 0; j < course[i].size(); j++) {
            cout << course[i][j];
        }
    }

    return 0;
}

Tried maybe the '\\r' removal by adding:

if (!line.empty() && line[line.size() - 1] == '\r') {
    line.erase(line.size() - 1);
}

But that just printed out each [i][j] per line next to one another.

Data looks like this:

xxxxxxxxxxxx
xxx   yyyxxx
xxxXXYYxxyyy

Answer 1

std::getline does not add the delimiting character (the newline in your case) to the output string. Thus, none of those std::string of your std::vector<std::string> course contains a newline. Thus you need to output a newline yourself after writing each of those strings.

Then please note that the inner for loop is completely unnecessary. There's an overload/specialization of operator<< for std::string , thus you can simplify to:

for (std::size_t i = 0; i < course.size(); ++i) {
  std::cout << course[i] << std::endl; // or '\n' if you don't need flushing
}

---

If you insist on the inner loop:

for (std::size_t i = 0; i < course.size(); i++) {
    for (std::size_t j = 0; j < course[i].size(); j++) {
        std::cout << course[i][j];
    }
    std::cout << '\n';
}

Live in action.