QGraphicsLineItem C++ code

Here is an example of how to create a `QGraphicsLineItem` in C++:

#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsLineItem>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QGraphicsScene scene;
    QGraphicsView view(&scene);

    // Create a line item with starting point (0, 0) and ending point (100, 100)
    QGraphicsLineItem *line = new QGraphicsLineItem(0, 0, 100, 100);
    line->setPen(QPen(Qt::red, 2)); // Set color and width of line

    scene.addItem(line);
    view.show();

    return app.exec();
}

This code creates a `QGraphicsScene` and a `QGraphicsView` to display the scene. It then creates a `QGraphicsLineItem` with starting point (0, 0) and ending point (100, 100), sets the color and width of the line using a `QPen`, adds the line to the scene using `addItem()`, and shows the view.