Question

I am implementing a tree which is a Binary Expression Tree. The leaf nodes are numbers, non-leaf nodes are math operators. Succesfully implemented printInorder,PostOrder, PreOrder, evaluate. But stucked with the printLevel().

Here is my int main ()

int main()
{
    EXTree myTree;
    string tests[] = {"2.1*3.1+4.2", "(2.0+1.3)/1.4", "2.*(1.3+1.4)","1.2*(1.3+1.4/0.5)","1.2*(1.3+1.4/0.5)-4.4", "1.2*(1.3+1.4/0.5)- (9/3)"};
    for (int i=0; i < 6; i++)
    {
        myTree.build (tests[i]);
        myTree.printInorder();
        myTree.printPreorder();
        myTree.printPostorder();
        myTree.printLevel(); //Starting from level = 0
        cout << "Evaulating myTree = " << format(myTree.evaluate(),2) << endl;
        myTree.removeAll(); // removes all the nodes
    }
}

printLevel(); only prints the level of the tree given above and its initally 0.

and here is my printLevel function.

void EXTree:: printLevel()
{
    queue<Node*> levelq;

    levelq.push(root);
    cout << "Current Level is: ";
    while( levelq.size() > 0 )
    {
        Node *cur = levelq.front();
        cout << cur->Root << "  ";
        levelq.pop();
        if (cur->Left)  levelq.push(cur->Left);
        if (cur->Right) levelq.push(cur->Right);
    }
    cout << endl;
}

But I really didnt understand how to implement the printLevel. Appreciate for any help to clarify it.

I just implemented the inOrder algorith to my printLevel and tried to change it but still didnt get it.

Answer 1

Since you have no problem with recursion, this would work without queue:

void EXTree:: printLevel()
{
    int currentLevel = 0;
    if (root)
    {
        cout << "Current Level is: ";
        printLevelHelper(root,currentLevel);
    }
    else
        cout << "This BST is Empty\n";
}

// Declare a private method:
void EXTree:: printLevelHelper(Node* &n, int &currentLevel)
{
    cout << currentLevel << ' ';
    if (n->Left)
    {
        currentLevel++;
        printLevelHelper(n->Left,currentLevel);
        currentLevel--;
    }
    if (n->Right)
    {
        currentLevel++;
        printLevelHelper(n->Right,currentLevel);
        currentLevel--;
    }
}