为什么这个名为“showTree”的 function 可以正常工作？

Question

This is the function that I don't understand:

void showTree (node ​​* tree, int cont) {
    if (tree == NULL) {
        return;
    }
    else {
        showTree (tree-> right, cont + 1);
        for (int i = 0; i <cont; i ++) {
          cout << " ";
        }
        cout << tree-> data << endl;
        showTree (tree-> left, cont + 1);
    }
}

I do not understand:

• How do you get to the for loop if that function is always called recursively?

• How are tree items displayed if that function is always called recursively?

If someone could explain to me how this feature works I would really appreciate it.

Answer 1

How do you get to the for loop if that function is always called recursively?

The function returns immediately if tree == NULL , so it may continue onto the for loop.

How are tree items displayed if that function is always called recursively?

The output is produced by the for loop and the next statement, so same reasoning.